 So let's talk about bacteria. Bacteria are obviously prokaryotes. They are relatively small. Now I found this visual for you to help you visualize different sizes with viruses. Seriously, look at these things. How tiny is a virus compared to a bacterium, which also is quite tiny. I mean, this is like two millionths of a meter. This is a really, is it a millionth? Yeah. Tiny, tiny little critters. Like thousands of them can fit inside a single eukaryote. This is a eukaryotic protist. So a single cell eukaryotic critter. And you can just see very easily the vast difference in sizes in these things. Now bacteria are unbelievably diverse. In fact, we don't really think of them as being diverse because they're all little single cells. But this is actually a bunch of bacterial cultures. This is something similar to what you would do in a microbiology lab. But these different critters right here are all a different kind of bacterium. And you can notice that the cultures or the little colonies that they create, each little dot is a bajillion bacteria. But they, because of the proteins that they're expressing, when they make their colony, the colony has certain characteristics. So you can see that there actually is even phenotypically some decent variation or diversity. However, most bacterial diversity comes from how they metabolize sugars. So the food that they eat, how they metabolize it. Do they go through some kind of cellular respiration? Do they use oxygen? Do they not use oxygen? Do they have an electron transport system? Like all of these things, we can actually test them. You can figure out the characteristics of bacteria based on how they metabolize their food. And when you start looking at that, then they're incredibly diverse. And I've got this fast fact for you, which is just going to blow your mind. Are you ready to have your mind blown? Always. If you took one gram of soil in Alaska, now Alaska is cold. It's definitely not a tropical rainforest. So it's kind of like frozen ground. One gram of soil. Now one gram weighs about a paper clip weighs about one gram. We're basically taking a paper clip's worth of soil from frozen earth in Alaska. There are 4,000 different species of bacteria in that gram of soil in Alaska. 4,000. Hopefully that blows your mind. You go to Minnesota and you go to like fertile farm soil in Minnesota and you do the same thing. Grab a gram of soil, 20,000 different species of bacteria, not just different bacteria. Not like, oh, I counted out 20,000 of these guys in this tiny paper clip of soil. No, I actually counted out 20,000 different species of bacteria. Bacteria are incredibly diverse. We don't really appreciate it because we can't see them, but I would like you to remember that. Now, we think of bacteria and we're like, ew, gross, bad. But some bacteria are very important. So we're going to talk about all the bacteria that are really good for you.