If the eyes are windows to the soul, they're open windows, potentially letting in all kinds of unwelcome bugs. To ensure that doesn't happen, our tears are loaded with microbe-killing compounds and immune cells. In fact, our eyes are so inhospitable that it was long thought they were the only part of our bodies which lacked a symbiotic bacterial community. But now, scientists have found evidence of a once-inconceivable ocular microbiome -- and it may help eyes fight off disease.