From Brainpickings: Our Microbes, Ourselves: How the Trillions of Tiny Organisms Living Inside Us Are Redefining What It Means to Be Human.

Being alone may be the central anxiety of our time but, as it turns out, you are never really alone — at least in a biological sense: Every single cell of you — that is, every cell made of human DNA — is kept company by ten cells of microbes that call your body home. And because microbes are single-celled organisms that each carry their own DNA, the difference is even starker in genetic terms — you carry approximately twenty thousand human genes and two to twenty million microbial ones, which makes you 99% microbe. What’s more, although you and I are 99.99% identical in our human DNA, we are vastly different in our individual microbiomes — you have only one in ten of my microbes. Even more striking than the sheer number of these silent and invisible cohabitants is their power over what we consider our human experience — they influence everything from our energy level to how we handle illness to our moods to how tasty we are to mosquitoes. [continue]