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. 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. Thanks for coming with me on this journey as we explore the unseen world that surrounds us.

And guess what, we have new merchandise! We have algae socks. We also have a new coloring book so you can spend a little time with your favorite microbes relaxing, zoning out, letting yourself just be for a little while.

Thank you of course to all of these people on the screen right now. They are our patrons on Patreon. These folks are what make this channel possible.

If you’d like to join them in supporting us, check us out at patreon.com/journeytomicro. If you want to see more from our Master of Microscopes James Weiss, you can check out. Jam & Germs on Instagram where you can see more great stuff from his new microscope.

And if you want to see more from us, there is always a subscribe button somewhere nearby.