In the two-hundred years since we discovered that microbes cause infectious diseases, we've battled to keep them at bay. But a recent explosion of scientific knowledge has led to undeniable evidence that early exposure to these organisms is beneficial to our children's well-being. Our current emphasis on hyper-cleanliness is taking a toll on our children's lifelong health. This engaging and important book explains how the millions of microbes that live in our bodies influence childhood development; why an imbalance in those microbes can lead to obesity, diabetes, asthma, autism, and reactions to vaccines, among other chronic conditions; and how-from conception on-parents can positively impact their own behaviors and those of their children. It describes how natural childbirth, breastfeeding, and solid foods influence children's microbiota and offers practical advice on whether to sterilize food implements for babies, the use of antibiotics, and why having pets is a good idea.