Our brand new diatom t-shirt is now up for pre-order over at microcosmos.store.

This shirt was designed by artist Josh Quick, and is a part of our Artist Series, which also features the recently restocked tardigrade and hydra t-shirts. And since it might be a little cold out there for just a t-shirt, we also just restocked the Homo sapiens sweatshirt.

Which I have and wear all the time. And you can find that and the brand new diatom t-shirt, along with microscopes, mugs, and more at microcosmos.store. We don’t often get a chance to reference the rest of the cosmos, so we’re going to seize the moment while we can.

When the astronomer Carl Sagan narrated the series “Cosmos,” he famously said the following: We are a way for the universe to know itself. Some part of our being knows this is where we came from. We long to return.

And we can, because the cosmos is also within us. We’re made of star stuff. Sagan was referring to the fact that our bodies are built out of atoms that are billions of years old, the pieces of stars that exploded and scattered into space, eventually settling into the matter that would form our earth and then our bodies.

But looking at these ciliates, it's tempting to take Sagan’s words more literally, to imagine that the little twinkles of light are actually stars… …that we dived so deep into the microcosmos that we have come full circle and stumbled on the cosmos itself. In place of a telescope though, we have a microscope, aimed at a million colorful constellations enclosed into their own galaxies and separated by membranes. But it takes more than just a microscope to see the microcosmos lit up like this.

James, our master of microcosmos, has to use a tool called a polarizer, which restricts the vibration of light traveling towards our samples. When this polarized light hits certain types of materials, the result is what we see here: shiny crystals. And as you might imagine, these intracellular crystals have fascinated scientists for centuries.

But the actual nature of these crystals—what they are made of and what purpose they serve— that has been much murkier. If you’ve been with us on our journey for a while, you’ve probably heard us say the phrase “we don’t know” a lot. The microcosmos does not guarantee answers, and we have often found ourselves looking at some unusual behavior or beautiful form that represents some fascinating, unresolved mystery.

And this has happened almost every time we have seen crystals in the microcosmos. We see them, we wonder what they are for, and then we move on to say “we don’t know.” But the great thing about science is that “we don’t know” is often a precursor to people finding a way to learn more. In the summer of 2022, a group of scientists published a paper in the International Society for Microbial Ecology describing their investigation into the crystal structures found within single-celled eukaryotes.

They used a technique called Raman microscopy, which combines a standard microscope with other tools—including a laser—to excite the molecules within a sample in ways that scientists can effectively read in plots and graphs that reveal the identity of those molecules. Every form of microscopy is a different way of seeing the microcosmos. And for the scientists working on this paper, Raman microscopy allowed them to search through more than 200 species of eukaryotes and identify the crystals within them.

Now some of these crystals were previously known. Molecules like calcite and oxalate and carotenoids. And more than 80% of the organisms they studied contained crystals made out of a type of compound called purines.

Purines are present in many types of compounds that are important to life: DNA, RNA, ATP…even caffeine. And in the case of these crystals, scientists found purines appearing in different forms like guanine and uric acid. For algae, the guanine crystals might function as nitrogen storage, helping the organisms weather the fluctuations in nitrogen available to them in the environment.

But there are also other types of crystals, and other types of organisms that live in different habitats with different needs, which means there are likely many other functions that we still do not know about. The ubiquity of purine crystals suggests that these types of crystals might be one of the oldest forms of biocrystallization, present in the last common ancestor to all eukaryotes. So what does this mean for our organisms?

Well… we don’t know. But identifying and characterizing these crystals is just the first step on a longer journey, one that will reveal more when we learn how to see what is right in front of us. And the more we learn about how these crystals form and function in these organisms, the more we will understand about the story of life on earth, and even about how our own cells work.

Because these crystals—removed as they are from the original star stuff they are made of—they still tie the cosmos and microcosmos together. They are beacons that do more than simply sparkle. They illuminate.

Microbes, they show us a way to know ourselves, a part of our being that knows this is where we came from. There is no need to return because we are already there. The microcosmos is within us, but more importantly, we are in the microcosmos.

We are made of star stuff that has made the same stuff: life. Thank you for coming on this journey with us as we explore the unseen world that surrounds us. Don’t forget to go to microcosmos.store if you’d like to pre-order our brand new diatom t-shirt, or pick up any of our other microcosmos products.

The money from that store goes right back into this channel, so when you pick up one of those cool Hydra shirts, you can know that you are are supporting what we do here. And speaking of supporting this channel, all the people whose names are on the screen right now, they are our Patreon patrons. They are the people who give a little bit of money every month and in exchange they get some cool stuff, but mostly I think the thing that they get is knowing that they're helping to make this little project continue to exist.

Uh, because of course without them, it definitely could not. If you are interested in joining them, you can check it 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.

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