One of the most mind-blowing things I learned about while writing my book Microcosm: E. coli and the New Science of Life was the incredibly diversity of microbes that call our bodies home. These microbes outnumber our cells by about ten to one, and collectively they have thousands times more genes than found in the human genome. E. coli may be the most familiar of these lodgers, but it is just small player in an inconceivably complex ecosystem on which our health depends. So I was very excited to interview Rob Knight of the University of Colorado, a biologist who's been co-authoring a string of stunning papers recently on the thousands of species that live on our skin, in our mouths, in our guts, and elsewhere on or in our bodies. Our conversation is now available on the latest "Meet the Scientist" podcast. We talk about how microbes help each other thrive in our bodies, the way bacteria in our guts release neurotransmitters, how microbes may regulate your weight, and much more. Check it out.