Hand sanitizer. Social distancing. Antibiotics. Fending off germs has long been considered one of the cornerstones of good health. But what if better health and more graceful aging actually went hand-in-hand with embracing the invisible microbes living on, in, and all around us? Our bodies are teeming with microbes—in the gut, yes, but also living on our skin, in our lungs, and beyond. They impact everything from our sleep, cognition, mood, heart health, and energy to our likelihood of developing dementia, diabetes, and some cancers. As groundbreaking new studies are showing, taking care...