[BASSLER:] Everything that you can actually see with your eye is just the smallest sliver of life on this earth. Most of life is invisible. We still have this idea that we're the most central feature of earth, and it's the humans that are the bystanders. The microbes are doing the work. [ANDERSON:] What do you do when you see things no one has ever seen before? L-A-Y. Lay. Ooo. VEN. They pronounce it with a 'V.' Who-keh. Leeuwenhoek. [PALM:] Antonie Van Leeuwenhoek. He was a haberdasher in the city of Delft in the Netherlands. [ANDERSON:] And why his curiosity found an outlet in microscopes, that is just lost to history. We really don't know. [PALM:] The quality of his microscope was superb. He made some 540 small instruments, and only a few of them he showed to visitors. He never told anyone how he made his lenses. [ANDERSON:] Robert Hooke, in England. He wrote this wonderful book, Micrographia [PALM:] The first observations of the small world with lenses. [ANDERSON:] One of the first things Leeuwenhoek did was to look at things that Hooke had looked at. There was the stinger of a bee. The leg I believe of a louse. Singular of lice. But he saw some things that Hooke didn't see because his lenses were better. It was summertime. It was August. The days are so long that you get a lot of algae growth on water. He called it "green clouds." Curious again, he has what he called a glass vessel-- you know, a jar probably-- and he filled it with the water. The next day, he put it under his lens, and what he saw was green streaks. Among this, was all these little animals. And these things were a whole lot smaller, like 1,000 times smaller than anything he had ever seen before. And I think the line is, "I confess I could not but wonder at it." [PALM:] Leeuwenhoek called them in Dutch "diertgens." And "diertgens," that's the diminutive of the word "dier." [ANDERSON:] Dier. D-I-E-R. [PALM:] Which is the Dutch word for "animal." [ANDERSON:] What Leeuwenhoek called them was "little animals." [PALM:] This was all so new. The word "microorganism" did not exist at the time. The word "bacteria" is from the 19th century. [ANDERSON:] And that strikes me as Adam in the Garden of Eden who in Genesis named all the animals. It was just a brand new world and he was the first person in it. [PALM:] He wrote a letter to the Royal Society, one of the first organizations to practice experimental science. [ANDERSON:] And they were going "Oh my heavens, what is this?" [PALM:] At first they didn't believe it. [ANDERSON:] Finally, the other members of the Royal Society were also able to see it, and the rest is history. [PALM:] And so he discovered many things. [ANDERSON:] Sperm, red blood cells, protozoa, and bacteria. [PALM:] Which nobody had ever seen before. [ANDERSON:] He is the first person to see everything he looked at for fifty years. [BASSLER:] Van Leeuwenhoek wanted to see these things, well he saw them. But now we get, most of life is microbial. You look at the tree of life, and only this tiny little part is every single thing you've seen. Every higher organism is covered, inside and out, with bacteria. And humans would not be alive if these little 24/7 partners weren't giving us all these genes and proteins that our own genomes don't encode. And they have all kinds of fabulous behaviors. Vibrio harveyi is a marine bacterium, it looks like a sausage, and it's very fast. Vibrio means vibrate. And what is amazing, is that if one watches them go from a single cell to a number of cells, all of the bacteria, in unison, start glowing in the dark. By studying this bioluminescent organism, we discovered that bacteria can communicate, using a molecular language. We used to think that social behaviors were the purview of higher organisms. What we now understand is that bacteria were probably the first organisms on this earth to ever communicate with one another. We're always looking at an unknown world. We're driven by our ignorance, and we're driven by the idea that the world must be more complex than what we understand right now. And that's enough inspiration to do an experiment. [BASSLER:] Can you imagine being the first one to see your sperm swimming around? That would be a scary thing, right?