Right now, you and I are watching a rotifer just chill and do its rotifer thing.

The long thin strands of cilia that make up its crown are whirling around to grab food, while the organisms around it are caught up and diverted by the vortex the rotifer has created. It’s a charming scene, as are so many of the other scenes we’ve witnessed come out of the microcosmos.

Whether you’re watching this at home or at work, we’re all sharing in these strange and delightful moments courtesy of our strange and delightful microscopic friends. And we don’t mean to add a layer of existential dread to the proceedings, but here’s something to think about: by the time you watch these scenes, the stars of the show that come in and out of view are most likely long gone. Perhaps they’ve been put back in the sample jar, or maybe they’ve died on the slide.

They may even have entered a protective cyst state. Whatever path their lives have taken since the moment they came into our view, we’ll never be able to create these exact scenes again. So we’re lucky today to have a way to preserve and share their lives in video.

And in the past, scientists turned to other artistic means to document the microcosmos, including illustration. But sometimes, pictures and videos aren’t enough. Sometimes the best way to share what you’ve seen under the microscope is, well, to share the actual thing you’re looking at.

These slides that you’re looking at right now were purchased from various auctions. Inside them are diatoms collected from around the world, some from Rio de Janeiro, others from England, and some from the Mediterranean Sea. These are places we might not be able to visit easily, and so who knows when we’ll be able to collect some of their microscopic residents.

But thanks to the fellow lovers of microscopes and microbes out there who collect and preserve their samples, we can actually see a bit of what they’ve seen with our own microscopes. These prepared slides are meant to be permanent. The goal is to be able to return to them at a later date, perhaps with fresh eyes or under a new microscope.

Maybe you’ve found a new species and want to save it for later observation, or to convince others that it’s truly real. Or maybe you’ve just found something that’s beautiful or cool, something that you think others will want to see and learn from. Whatever the motivation, the results—as you can see here—are often stunning.

Now there are many ways to prepare samples for microscopic study because there are many different types of specimens to sample—from microbes to pollen to organs. When we study our own samples here, we’re using what’s called a “wet mount”—our little buddies are swimming around in a liquid, in this case water. We apply a bit of this watery sample to the slide, enclose it with a coverslip, and then we observe.

But to make these slides permanent, the microscopist has to do things a little differently. Again, these techniques can vary, but if we were to follow one set of instructions we found to prepare a permanent diatom sample, we’d start by allowing our watery microbe mix to settle on a coverslip until the thin layer of water has evaporated away. Then we would add a mounting medium to the slide and turn the dry, diatom-coated coverslip onto it, allowing the medium to seep in and preserve the organisms left behind.

We are definitely simplifying this process for narrative effect. But we want to note that because of the volatile compounds in the mounting process, the instructions also contain a specific note to perform this procedure in a fume hood (among other safety precautions). So we recommend that anyone seeking to make these prepared slides do a bit more research on the best and safest methods for their needs.

You may have noticed already that the diatoms we are watching in these prepared slides bear a strong resemblance to the living diatoms we’ve watched countless times on this channel before. But they’re also a bit different, with the colors and shapes shifted just slightly, as if we’re watching them through a filter. This is likely due to the use of acid to remove their organic parts, erasing much of their biological contents from our view, but leaving behind the stunning silicon frustules that diatoms encase themselves in.

The result feels a bit like roaming through the dioramas in a natural history museum, with scenes from nature rendered on the other side of the glass to suggest a living world that does not actually live. Those dioramas have the stillness and sense of distance that a photograph does, but they are also their own direct experience that is shaped by the setting you observe them in. In that same way, these permanent slides are their own unique perspective of a static microcosmos, informed as much by the people who made them as they are by their later observers.

And these slides have been letting microscopists preserve and share the objects of their fascination for centuries. Around the mid-1800s, microscopy became kind of a thing—particularly in Britain. Manufacturers were producing more affordable microscopes, and users were publishing guides to help others use this tool to navigate the unseen world.

Amateur and professional microscopists began to form groups like the Quekett Microscopical. Club, united by the curiosities on the other side of the lens. The slides they prepared carried everything from beard hairs to insect exoskeletons to diatoms.

And more than a century later, people still collect these slides, studying their contents not just to observe the worlds mounted within them, but also to understand the people who made them. And just as art museums have to verify and conserve the works produced by old masters, museums and collectors have to handle these microscope slides with care. As one collector noted, these slides can sometimes sell for thousands of dollars, attracting forgers whose false work becomes apparent in fonts that are too modern and cuts that are too uneven.

And the authentic slides require maintenance as well, whether their surfaces need to be cleaned of grime or their contents re-preserved. The fascination and attention these centuries-old slides inspire feels like a natural extension of microscopy both as a hobby and a scientific pursuit. We’ve heard from many of you that the footage we share on this show has made you want to buy a microscope, to sample the world around you to see what it contains.

And what are these slides except just another way microscopists have been sharing the natural world with each other? These slides don’t show us the microcosmos as it once existed as much as they reflect the journey the microcosmos itself has taken, through solvents and hands and elements. Through microscopists and collectors.

And then, of course, to you. Thank you for coming on this journey with us as we explore the unseen world that surrounds us. And thank you especially to all of the people here on the screen right now who are some of our supporters on Patreon, where we now have a $2 tier that includes access to a Journey to the Microcosmos Discord.

And if you want to learn more about that you can go to patreon.com/journeytomicro If you want to see more from our master of microscopes, James Weiss, check out Jam & Germs on Instagram. And if you want to see more from us, There’s always a subscribe button somewhere nearby.