So that bag of flesh and bones you call your body is actually made up of something like 10 trillion individual cells, all working in concert. Pretty impressive, right? Well, try this on for size: You've got around 100 trillion microbes living on and in you. You're your own biome.That first stat is how Joe Hanson opens this episode of It's Okay To Be Smart, which is dedicated to the human microbiome. As he notes, it's kinda silly that we're all so obsessed with antibacterial sprays and lotions when we're covered in tens of trillions of microbes to begin with. (Washing your hands is still a good idea, as the microbes living on us generally don't make us sick like the ones we pick up off subway handles and whatnot do.)When we talk about biodiversity, we often forget the incredible wealth of microbial diversity out there. (I'm guilty too; I learned quickly in my studies that if I can't see it with my bare eyes, I won't remember it.) But the diversity is huge. A recent, widely-discussed study found nearly 1,500 new species of bacteria in people's belly buttons. Mix that in with all the rest of our bodies, and you've got a whole lot of little creatures cruising around and living off the fat of your land. Feeling icky yet?Fear not. As Hanson notes, this microbiome plays a huge role in the development of our immune system, and as we grow, we develop a pretty mutually-beneficial relationship with all of the microbes living on and in our bodies. For example, some gut bacteria help us extract vitamins and minerals from our food, while the ones that make us sick usually get fought off.In fact, our microbiome is so important that it's one of the largest constraints in developing new antibiotics. Broad spectrum antibiotics can be good at killing off all kinds of bacteria, but if you drop a nuclear gut bomb, you'll end up also killing off all of the beneficial bacteria we need to survive. In fact, losing those microbes is the reason some people must undergo fecal transplants, which aren't pleasant. So yes, you're home to trillions of little microbes that live off you. But be happy that's the case, as we humans wouldn't be able to do what we do without them.@derektmead