Don't look now, but roughly 100 trillion bacteria live in and on your body. According to scientists, these microbes—especially the ones in your gut—may be fending off chronic diseases, moderating your weight, and strengthening your immune system. But our society's processed foods and war on bacteria are posing a threat to these bacterial squatters, writes Michael Pollan in the New York Times Magazine. "As a civilization, we’ve just spent the better part of a century doing our unwitting best to wreck the human-associated microbiota," he writes. A few highlights: