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Go to https://microcosmos.store before August 8th to get 10% off of almost everything in the store and to pick up a limited edition Dark Mode Hydra T-Shirt!

This channel wouldn’t be what it is if it weren’t for one very key invention: the microscope. Everything we see, we see with the aid of light and lenses, expertly deployed by our master of microscopes, James. And if you’ve been on this journey from the beginning, or if you’ve ever gone back to revisit our earlier videos, you may have noticed that things have changed a bit around here.

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SOURCES:
https://micro.magnet.fsu.edu/primer/anatomy/magnification.html
https://micro.magnet.fsu.edu/primer/anatomy/sources.html
https://www.geog.ucl.ac.uk/resources/laboratory/light-microscopy/bright-field-microscopy
https://micro.magnet.fsu.edu/primer/techniques/darkfield.html
https://micro.magnet.fsu.edu/primer/java/darkfield/cardioid/index.html
https://www.microscopyu.com/techniques/phase-contrast/specimen-contrast-in-optical-microscopy
https://micro.magnet.fsu.edu/primer/techniques/phasecontrast/phase.html
https://www.microscopyu.com/techniques/polarized-light/introduction-to-polarized-light
https://www.microscopyu.com/techniques/polarized-light/polarized-light-microscopy
https://www.microscopyu.com/tutorials/comparison-of-phase-contrast-and-dic-microscopy
https://www.microscopemaster.com/differential-interference-contrast.html
https://www.microscopyu.com/techniques/fluorescence/introduction-to-fluorescence-microscopy
https://www.microscopyu.com/microscopy-basics/introduction-to-microscope-objectives
https://www.olympus-lifescience.com/en/microscope-resource/primer/anatomy/magnification/
https://www.microscopyu.com/tutorials/nuaperture
https://www.microscopyu.com/microscopy-basics/refractive-index-index-of-refraction
Starting today, we arre having a 10% off  Back-To-School sale over at microcosmos.store.

So whether you are decorating a new dorm room  or classroom, or you’re just trying to   decide what to wear for your first day of  school, microcosmos.store has you covered. We’ve got t-shirts,  sweatshirts, pins, and posters.  And we’ve got our Microcosmos  microscope, slides and coverslips,   and even a Microcosmos microfiber cloth  to keep everything nice and clean.

And this week only, from now through August  8th, almost everything in the store is 10% off!  And that’s not all, we’ve also got this  new Dark Mode version of our Hydra t-shirt   that's only going to be available  during this sale and then never again. So, head over to Microcosmos.store  to check out the sale and to pick   up your limited edition Dark Mode Hydra T-Shirt This channel would not be what it is if it weren’t  for one very key invention: the microscope.   Everything we see, we see with the aid  of light and lenses, expertly deployed   by our master of microscopes, James. And if you’ve been on this journey from   the beginning, or if you’ve ever gone back to  revisit our earlier videos, you may have noticed   that things have changed a bit around here.

Everything we can see is a function of the tools   we use. And as we’ve explored new microscopes  along with other new tools and techniques,   that means we’ve been able to see the microcosmos  differently. Colors have changed, contrast has   deepened, and sometimes things even sparkle.

So today, we’re tracking our journey… through   our journey. We have compiled the videos we’ve  made that focus on how our microscopes work   and the ways we have improved our methods over time  so you can see how much of microscopy is an art—an   art that uses light in incredible  ways that only physics could predict.  So to start, let’s go back to an  early video, where we went through   the different methods we used at the start of  our channel to illuminate our samples. Think   of it like an introduction to optics, told  through the bodies of tardigrades and algae.

This is a ciliate, just a eukaryotic microbe  waving its cilia around under our microscope. This is the same ciliate. And yup, here it is again… …and again.

But as you’re probably noticing,   while the rough outline of this organism seems the same from shot to shot,   the ciliate itself and the world around it clearly  look very different from shot to shot. Colors   change, details are more apparent. In one  case the organism seems lit from within.

On this channel, we're constantly flipping between  different ways of capturing images of organisms.   So which one of them is what they  actually look like? Well...none of them. Anything you see through a microscope is an image  —which in our case, means that everything we   show you on this channel, every frame, is not the microbial world itself.   It’s an interpretation of life on the other  side of our objective, translated through the   lens into details, shapes, and colors—all affected  by the way we light up the life we want to see.

Light is amazing, it’s also very weird.  It travels in waves, and as it interacts with   particles and materials, it scatters, shifts. Even  if we can’t actually see those light waves in motion,   so much of what we observe in the world  around us is rooted in the physical properties   that define those waves—like how we can observe  certain frequencies of light as colors. But waves   have far more to them than  just their frequency, and microscopy   has combined the resourcefulness of many  different sciences to use light to give us   different ways to peer into the microbial world.

So let’s start simple with the good old fashioned   white light. Early microscopists used oil lamps  and sunlight to see through their microscopes,   and while the technology has changed, the  simplicity of this has endured into   the modern technique of brightfield microscopy. It all starts with a source of light, though   modern microscopes have their lamps built in, set  up underneath the stage that holds our sample.   Light travels from the source through  a condenser, which works to focus   the light onto the sample above it.

This focused light travels through the   sample towards the objective lens, which takes  in an image and magnifies it into these bright   backgrounds with organisms, sometimes rendered  transparent by the intensity of the light. You might say that this is as close as we get  to seeing what the microcosmos actually looks like,   but that would be like taking 2000 watt  light bulb into your living room and saying,   “this is what my home looks like.” Light affects  things, and we are not shining light on these   organisms, we’re shining light through them. Now, brightfield might seem relatively simple,   but that simplicity has been incredibly powerful  in allowing scientists old and new to wade through   microscopic waters.

Still, there are limitations  to consider with any scientific technique,   and one of the major challenges for  brightfield microscopy, particularly   when we’re looking at microbes, is contrast. Pigmented organisms are easy to visualize against   the bright background, but in cases where  the organism has been rendered transparent,   it can be harder to distinguish their bodies  from the rest of the world they inhabit.   Scientists can navigate these challenges using  stains that make certain structures more visible,   but for our purposes, we like to avoid stains  because they can affect the microbes themselves. There are ways to contend with this challenge,   one of which is built on one of those  simple-yet-strange properties of our world:   you don’t always need to shine light directly  onto an object to see it.

This technique is called   darkfield microscopy, which sounds like it  must be the opposite of brightfield microscopy. It’s not. The two techniques  are actually very similar:   light travels from a source through a condenser,   interacts with the sample, and then travels into  the objective lens, producing the image we see.

But what we want in darkfield microscopy is for the  beam of light to hit the sample, but not our eye.   In darkfield microscopy, a circular  disk is placed inside the condenser,   blocking the central part of the light light from  shining through the sample and into our eye, or,   our camera. This means that when there is no  sample on the slide, all you’ll see is black.   But the disk doesn’t block all light: there  is still a hollow cone of light that travels   around the disk, unable to reach the objective or  our eyes, but that light still hits the sample.   When it does, their microscopic, transparent  bodies scatter those hidden rays into our view. And as they do, an image of their  bodies forms against a dark background,   providing us with this almost cinematic footage.

Another method to get better contrast than   brightfield microscopy is called  phase contrast microscopy,   and it’s built on working with a property of  light that we can’t actually directly experience. Microbes , or really anything, that is easily  visually observed with brightfield microscopy   are called amplitude objects because  as light passes through them,   the amplitude of the light wave changes,  which we see as changes in light intensity. But there is another class of specimens: these  are called phase objects.

As light passes through   these objects, the waves slow down and shift  slightly in phase compared to the unaffected light   around it. And if you’re wondering what that means  in terms of what we can see, that’s the issue:   our eyes don’t process these differences  in phase. And so in the final image,   these objects, or in our case,  organisms, are very difficult to see.

In the 1930s, a physicist named Frits Zernike  developed a method to shift the direct   light just slightly enough so that these  changes in phase could actually be translated   into changes in amplitude, producing  an image of these formerly hard-to-see   phase objects by essentially treating them  as amplitude objects. There is a lot of   physics to this that we are glossing  over, but the result was so important   that it would eventually win Zernike the  Nobel Prize in Physics. And of course,   selfishly, we appreciate his work because it lets  us see more of our more hidden microbial friends.   And for the last type of microscopy we’ll go over  today, we’re going to be getting into another   property of light that we can’t directly  see, but that makes the microcosmos glow.   Most of the light we see has an electrical field  that vibrates in all sorts of planes relative to   the direction the light is traveling in.

But  that vibration can be restricted to one plane,   and when that happens, the light is said to  be polarized. We[8] can’t see the difference   between polarized and unpolarized light.  You might notice the difference in how the   world looks when you’re wearing polarized  sunglasses, but these are changes brought   about by changes in color or intensity,  not the polarization of the light itself.   So when does polarized light help us  in microscopy? Well, a lot of materials   stay the same optically-speaking, no matter what  direction you shoot light at them with.

But there   are certain materials where specific properties,  like how fast light travels through them, can vary   depending on which way the light is striking them.  These materials. called optically anisotropic,   can also take in a ray of light and  divide it into two separate beams.   By aiming polarized light at our sample  and then reconstructing an image based on   how the various parts of the organism  interacts with that restricted light,   particularly by how it might cause the light  to split, we can see more of these optically   anisotropic materials in action. In our case,  it often takes the form of shiny crystals.   So we’ve given you the big overview of  what these different techniques can do,   let’s go back and review what that means  for the original ciliate we started with.   This is the ciliate under brightfield microscopy.  The background is bright, the image produced by   changes in light amplitude that allow us to see  the overall shape. But some of the detail is hard   to make out.

Under darkfield though, the contrast  increases and some of these details become more   obvious, displaying compartments and cilia in  greater detail that are also apparent under   phase contrast. And then under polarized light,  the crystals that blended in with the organism   previously are now quite visible and vibrant. There are, of course, many other microscopy   techniques, but we think it’s incredible that  with just these four, the world of the microcosmos   looks almost like different universes,  wrapped up in one invisible world   around us.

The journey, it seems, is not  just about what you see, but how you see it. And ultimately, none of these views are  what the microcosmos actually looks like,   either that, or all of them are. Our brains play  tricks on us to make us believe that the world   looks one way, but the world looks different  at night than in the day, and both of those   things have more to do with the physiology  of our eyes than their objective reality.

Asking what microbes look like is, to  some extent, forcing our own experience   onto something that is beyond it. Which is  not something I ever would have thought of   if it weren’t for this little YouTube channel. Now we have been really fortunate over the years  to have the support of so many people,   and to be able to direct that support  back to the microscopes we use.   In 2020, we introduced James’ new microscope,  which he was able to buy thanks to crowdfunding.   This was our first major microscope upgrade on  the series, and it’s incredible to see the jump   in quality and how it compares to the different  techniques we showcased in the previous video.

This golden algae is swimming around  in water and white light, illuminated   from below using a brightfield microscope. And here we have that mallomonas sample,   filmed a day later using a different  technique thanks to a brand new,   freshly installed microscope. When James, our master of microscopes,   saw them for the first time, he got a little  emotional because, to quote him directly,   “the thing I know so well, was looking  so so much different than usual.”  Those differences in how the mallomonas look are  due to a type of microscopy called “Differential   Interference Contrast.” Or…DIC.

Earlier this year, James started   a crowdfunding campaign to purchase a  new microscope, one that would allow him   to use differential interference contrast  to produce these images you are seeing now.  Now technically, “differential interference  contrast” is not a type of microscope. Rather,   it’s a method that enhances contrast. And as you  can see, the final product is an image that seems   almost 3-dimensional.

Just watch this stentor  coeruleus as it swims across the slide. Its   cilia are so prominent that  it almost feels like you can   touch their vibrating fuzziness. And  the striations down its body are so   sharp that when the stentor contracts, it’s  like you can feel it pushing inward and then   back out again.

I don’t know about you,  but it’s almost like you could reach out   and touch it—like you’re in a movie theater  with 3d glasses on, reaching out to something   that seems to be reaching back out to you. Differential interference contrast microscopy   was invented by Georges Nomarski in 1952,  building off the principles underlying phase   contrast microscopy, which is a different though  similar thing. But both of these methods work   to translate invisible shifts in light phase that  can happen when studying certain samples into   visible changes in light amplitude, which we see  as changes in light intensity.

And as a result,   both techniques enhance contrast and let us see  parts of the microcosmos that might be invisible   with regular brightfield microscopy. But phase  contrast microscopy and DIC shift and work with   light in different ways to accomplish this goal. How do they do it?

Well, if you’ve ever taken an   optics course, you will remember how terrible  that was. But, very basically, phase contrast   and DIC are two ways to take advantage of  a strange reality. Light actually travels   further through some materials than others.

Kinda.  The optical path length is a function of both   the distance between two points and the refractive  index of the material the light is travelling   through. Basically, denser samples have longer  optical path lengths. Phase contrast microscopy   takes advantage of that, making areas with  longer optical path lengths look darker.  DIC on the other hand, doesn’t make areas  that are denser darker, it uses some very   cool optics to create sharp contrast in areas  of rapid change in the optical path length.   So, the faster the gradient from more to less  dense or vice versa, the more contrast you see.  But it’s also important to note that  while these images are the result of light   traveling through a sample, they are not  an actual topographical map of an organism.  DIC microscopy is a technique, but it does require  certain physical additions to a microscope.

For   one thing, we need to split light apart. So,  first we have a prism that splits polarized   light into two orthogonal rays of light that will  then pass through the sample and interact with it   in different ways. And then there’s a second  prism that recombines those two rays after   they’ve traveled through the sample, forming an  image based on the differences those two beams of   light experienced for our eyes and cameras to see.

In addition to these prisms, this technique relies   on having higher quality objectives than what  we’ve been using in the past. The objectives are   the little lenses at the bottom of the microscope  that actually do most of the magnification. Not   many people would realize this, but the objectives  we use for Journey to the Microcosmos are some of   the cheapest and most common types of objectives,  they’re known as achromatic objectives.

But while   these objectives produce so many of our favorite  images, James needed a microscope update to be   able to do differential interference contrast. So with help, perhaps including some from you,   James bought a new Zeiss microscope. It took eight  weeks for it to arrive, which is a long time to   wait.

But luckily the manufacturers sent him a 150  page manual to occupy his time until it arrived.  When the microscope finally showed up, James still  had to wait for an engineer to install the nearly   50 pound machine. But he didn’t waste any time.  James went out to gather his precious Mallomonas   and prepared a slide that night, keeping it stored  in a humidity chamber so that he could look at it   as soon as the microscope was ready. The next day, the Zeiss engineer took   3.5 hours to put all the pieces together  and set everything up.

But from there,   well, it was all on James to observe what he  could and experiment with his new microscope.  Some of his experimenting has been geared towards  making sure that he can get the best image   possible. These objectives have a much smaller  working distance compared to our previous ones,   and so you need to prepare the slides  a lot thinner to get a sharper image.   So even for our master of microscopes,  there was somewhat of a learning curve   to make sure he was getting videos that  were as sharp and vivid as he wanted.  But some of the experimenting is  based out of that most exciting thing   of all: curiosity. He’s removed some of the  prisms to see how it affects the footage,   and added a magnifying glass over the light  source to scatter the light in different ways.  That’s the joy of the microcosmos.

It is so  infinite. There’s it’s own objective existence,   full of so many more organisms than  we’ll ever be able to identify.   But there’s also the infinite  nature of how we experience it,   of how our own view of this world is shaped by  the many different tools we use to observe it.  And maybe that’s the case all  the time...that what we see   is as much about how we view the world as it is  about the world itself. The same thing with a   different lens, a different technique, a different  base of knowledge, can look completely different.

As we start our third season of Journey to the Microcosmos, we hope you will continue to join us through both our new and old lenses, as we uncover more of this hidden, unending world. In 2021, James went all out on improving his  toolkit, investing in higher quality objectives,   a polarizer, and the equipment he needed to do  fluorescence microscopy. If you’re not sure why   those things had all of us on the Journey  to the Microcosmos team so excited, well,   that’s what our next video is for.

You will get to  see just how much of a difference an objective   can make, and why electrons jumping up and down  can reveal a whole new side to the microcosmos. We’re nearing the end of our fourth season of  Journey to the Microcosmos, and over that time,   we’ve been able to see microbes through  all kinds of lenses—literally—thanks   to James, our master of microscopes. For  the rest of us on the Microcosmos team,   it’s been really cool to not only see  the footage that James has recorded,   but also see the journey that he has  been on with the microscopes themselves.  Now, we’ve been able to make this journey  because of all of you and the support you   have shown to this channel by watching and  commenting and sharing with others, or even   and especially by supporting us on Patreon.  We’ve all been on this journey together, so   let’s look back on where it’s taken us, and also  get a peek at where we’re going in the future.  In the first season, James started out with  two microscopes.

One was a microscope that   he assembled himself from different parts for  under $200. The other microscope was a Motic   BA310 that he received from a microscope  company shortly after we started this channel.  And these microscopes give us so much beautiful  footage, thanks in part to the different   techniques that James used with them, whether that  was bright-field or phase contrast or darkfield,   or some other technique to manipulate  the light shining on the microcosmos.  But these microscopes also had their  limits, so we were really excited to see   what would happen when James bought a new  microscope before the start of our third season:   the Zeiss Axioscope 5. This new microscope  came with higher quality objectives (which   are the lenses on the bottom of the  microscope), as well as prisms that   made it possible for us to look at microbes with  differential interference contrast microscopy,   a technique that sharpened their features and made  them seem more three-dimensional on our screen.  We have videos exploring these different  techniques and microscopes, so if you want to   learn more about them, we recommend checking those  out because light is much weirder than it seems.   But we wanted to do a quick summary for reasons  that are probably very clear from the title   of this video: we have upgraded our microscope!

The Zeiss Axioscope 5 was a very exciting change,   but it was also an expensive one. So when James  bought it, he was only able to get two objectives:   a 20x objective and a 63x objective. Adding that  to the 10x magnification the eyepiece gives,   let us magnify our samples by 200x and 630x  respectively, which is not bad.

But a standard   microscope usually comes with 5-6 objectives for  a reason: the microcosmos is full of things both   small and large to observe and there  isn’t a one-size-fits-all objective   that you can use to observe everything. So one of James’ priorities was expanding   his set of objectives so that he could have  the flexibility to see the microcosmos at more   scales. And thanks to his recent upgrade,  he’s now gone from a set of 2 to a set of   six that range from 5x to 100x and that gives  us a magnification range from 50x to 1000x.  Since I have gotten my own prototype  of the microcosmos microscope that   we are manufacturing thanks to backers of our  kickstarter, I’ve been amazed at how important   it is to have this variety of options, and how  much time I spend on the lower magnifications   and well as going deeper .

So without further ado,   let’s introduce these different objectives by  looking at a ciliate called Tetrahymena that’s   taken up residence in a rotifer exoskeleton. With the 5x objective, we can see   little dots swimming in what used to be empty  space, but it’s hard to make out the details.  When we move to the 10x objective, we can  start to make out shapes of the Tetrahymena   and more of the emptiness around them,  but it’s difficult to see the exoskeleton.  Then as we start to go up in magnification,  the details of the exoskeleton become clearer.  It's cool to see more and more of those details  as we zoom in. And especially when we get to   the 100x objective, which gives us 1000x  magnification, you can make out so much of   the insides of the Tetrahymena, that they  look like bags of very resilient bubbles.  Here’s another ciliate called a Pseudoprorodon  that James looked at through all of these   objectives.

At first it just looks like a little  green thing floating around and knocking into   stuff. But as we go up in magnification, we can  start to make out the subtle undulations of its   body, which shifts the different shades of green.  And as we look even closer, the green itself takes   on a new life, revealing the perimeters of the  individual algae inside the pseudoprorodon.  Revealing those details inside the tetrahymena  and pseudoprorodon comes at a cost. We can’t   see as much of the world around them,  whether that’s the emptiness around the   rotifer exoskeleton or the objects that  the pseudoprorodon keeps bumping into.  Whether or not you need those details depends on  what you’re trying to learn or what we are trying   to show, and that’s why having the flexibility  to look through a wider range of objectives   is such an exciting upgrade for us.

Objectives are  our gateways to the microcosmos, and we’re excited   to have all of these new scales to look at. We’ve also made some other upgrades so we can   revisit techniques we used on our older  microscopes. Like a polarizer, because   who doesn’t love this shiny, iridescent stuff?

But we’re not just sticking with what we’ve   known. Thanks to this upgrade, we’ve got a  whole new way to look at cells: fluorescence   microscopy. And we are so excited for this one.

The techniques we’ve highlighted so far   are all clever manipulations of white light, a  mixture of many visible wavelengths of light. But   in fluorescence microscopy, instead of  illuminating our sample with that mixture,   we choose a specific wavelength of light. That light is called the excitation light   because, well, it excites certain  structures based on their chemistry.   And those excitable structures then emit some  light of their own.

The emission light will   then travel back through the objective, get past  barriers that filter out the excitation light,   and then show up in our eyes as vivid color. With our upgrade, we have four different   wavelengths of light that we can  use for fluorescence microscopy,   and the parts of the sample that we see  fluoresce will depend on which light we use.  In this footage, we’re looking at the  Pseudoprorodon that we saw earlier, only   this time it’s being hit with 385 nanometer light.  The red we see is the fluorescence from natural   structures, this is called autofluorescence.  The rest of the organism is dark because   it did not respond to that 385 nanometer  light, making the color all the more vibrant.  But the power of fluorescence microscopy is  not just finding fluorescent structures that   exist in nature. Chemists and biologists  have developed all sorts of ingenious   techniques to highlight different parts of  cells using fluorescent dyes and proteins.  James is working on building up his arsenal of  fluorescence microscopy tools and techniques   so that soon, we’ll be able to dive even deeper  into the microcosmos to seek out things that have   been hidden from us before, uncovering the unseen  world inside the unseen world that surrounds us The upgrades we’ve talked about in  the last few videos have involved   fancy equipment and exciting techniques.

But light   is so weird and powerful that sometimes you don’t  need anything particularly fancy to make it do   something useful. Sometimes you just need  the right objective and a little bit of oil. If you’ve been following along with us lately,  you probably know that we’re pretty excited   about our latest microscope upgrades.

And can  you blame us? It's like having a new toy that’s   actually a spaceship. It’s pretty hard to  shut up about something that is shiny and new,   and also takes you into a whole new world.

And that’s kind of what it feels like to see   our familiar friends at this magnification. Even  though we’ve seen tardigrades many times before,   in so many different ways, we  have not seen them like this.  And bringing this level of magnification gives  us a new layer of the microcosmos to explore.   It’s like we’ve descended into a new level of  a cave, getting further from our world—though   fortunately for the easily scared among  us, the cave is metaphorical and the risks   are negligible. All we need for the journey are  some objective lenses and a tiny drop of... oil?  Yeah, oil.

But to explain   what that oil does, we’re going to have to  get a little technical first. Because yes,   we love our microbes, but we’re only able  to see them thanks to light, and light   is complicated, but we need to give it its due. So let’s start with the objective lens.  The main job of the objective lens  is to take light leaving the sample   and focus it into an image for the us  to see.

And there are two main numbers   that describe the objective lens. The first one’s  pretty obvious: it’s the magnification. But the   magnification you see written on the objective  lens is not the same as the magnification we   write up on the corner of the videos.

That’s because the objective lens isn’t   the only source of magnification in our  microscope. We’re also looking through an   eyepiece that has its own magnification. So the  final magnification that we see is the product of   the objective lens’ and eyepiece’s magnifications.

Now we don’t usually do math on this channel,   but this is one of the rare cases where  the math and optics is straightforward.  In our microscope, the eyepiece has a  magnification of 10x. So if we’re looking through   a 63x objective, the final magnification is 630x.  And that is the number you’ll see in the corner.  But you should never trust an optics lesson that  seems simple. How could it be when the image we’re   seeing is the product of so many things at once,  some tangible like a lens, others much less so.  And what is less tangible than  light, which is, as we’ve seen before   on this channel--a very strange thing.

We  cannot touch it, but we can manipulate it,   using what we know of the way it travels and  bends and reflects to see our world differently.  But light… has its limits. The thing about  making things larger is that at some point,   it’s not enough to just zoom in. You need to  be able to capture the detail that’s there.  And this leads to the second important  number you’ll find on an objective lens:   the numerical aperture.

Unlike magnification,  “numerical aperture” is probably not super   self-explanatory. What the number describes is  the ability of the objective to take in light.  As light travels from the sample and to  the objective, it radiates outwards like   a cone. The higher your numerical aperture, the  wider the cone of light that's going into your   objective.

And that allows for more rays to enter  the objective from all sorts of different angles,   helping to illuminate more details and give  greater resolution to your final image.  But of course, that’s still not all that goes  into capturing the perfect microscopic image.   Let’s take a look at this glaucoma spinning around  at 1000x magnification. It’s visible, and you can   see some of the details. It looks…fine.

But let’s take a look at it again here.   Same glaucoma. Same objective. Same level  of magnification.

What was “fine” before   now just looks dull in comparison to the image we  were seeing before with the detailed striations   and vivid pockets of green on the glaucoma’s body. To get from one of these images to the other,   James—our master of microscopes—didn’t change  any of the technical settings on his microscope   or pull some kind of video editing wizardry. He  just simply added a drop of oil to the coverslip   encasing the glaucoma, and dipped  the objective into the oil.  Now this is because the cone of light going from  the specimen into the objective isn’t just going   straight from the sample to the lens.

It’s passing  through something—it’s passing through air.  Light travels at different speeds through  different materials and when it changes   from material to material, it will bend. This  is called refraction and materials like oil   slow light down more. And that matters to our microscope   because it gives us the wider cones of light  we need to get a higher numerical aperture.  Whether we’ve got air between the sample and  the lens or oil when we’re viewing our samples   depends on the objective we’re looking through.  Our lower magnification objectives have   lower numerical apertures, and they’re meant  to be used with air.

Our higher magnification   objectives have higher numerical apertures,  and they’re meant to be used with oil.  Using air with oil objectives gives us poor  images, and using oil with our dry objective   would damage the objective. So…don’t do that. The numerical aperture and its relationship to   resolution is important because it puts a limit  on just how much magnification we can actually do   with a given objective.

There’s a general estimate  if you are looking into microscopy yourself,   that you’ll get a good magnification when you’re  working in the range that’s 500 to 1000 times   the numerical aperture of the objective. So our 100x objective and 1.3 numerical aperture   can reach a maximum of 1300x magnification  depending on your eyepiece. With our 10x eyepiece,   we get 1000x magnification, and it works great.

But if we tried to get more from this set-up by   increasing the magnification of our eyepiece  to 20x, we could not actually get 2000x   magnification. Because of the constraints  of our numerical aperture, we would just   be losing half of our image without actually  gaining more detail in what’s left to see.  But that’s what happens any time we want to  take an image: we have to make a decision   between what we can and cannot see. There are  always choices that have to be made, and details   that have to be lost.

We simply cannot see all  of the world, in all its entirety, all at once.   But we can see more of it by tracking the choices  we make as we dive deeper, choices in techniques   and materials that affect what we can see and  how we see it, and enrich the story further,   even when those choices impose constraints. At some point in history, we wanted to see more,   and lenses with their magnificent manipulation of  light have helped us do that. We’ve used them to   see light from distant stars, and to peer into the  most mundane surroundings on earth.

And whatever   image has come back to us has brought the universe  closer to view, even if it’s just in fractions. Thank you for coming on this journey with us as  we explore the unseen world that surrounds us. And remember, if you’re watching this before  August 8th, you have until then to check out   our back to school sale at microcosmos.store.  Almost everything in the store is 10% off right   now and we have a limited edition Dark Mode Hydra  t-shirt that’s only available during the sale.

So check out microcosmos.store before August  8th if you want to get your hands on one. All the people's whose names are coming up on the  screen right now, they are our patrons on Patreon. They are the reason that we are able  to continue exploring this beautiful   unseen world that surrounds us.

There  is so much left to explore and I am so   excited to continue exploring it  with you and all of our patrons. And if you would like to become one of these  people you can go to Patreon.com/JounryToMicro. If you want to see more from our  Master of Microscopes, James Weiss,   and why wouldn't you?

You can check out  Jam and Germs on Instagram or on TikTok. And if you want to see more from us, there is  always a subscribe button, somewhere nearby.