This month has seen a flood of new studies and reviews on the microbiome, the collection of creatures that call our bodies home. In tomorrow’s New York Times, In tomorrow’s New York Times, In tomorrow’s New York Times, I look at why scientists are going to so much effort to map out these 100 trillion microbes.

The microbiome is not just an opportunistic film of bugs: it’s an organ that play an important part in our well-being. It starts to form as we’re born, develops as we nurse, and comes to maturity like other parts of the body. It stabilizes our immune system, keeps our skin intact, synthesizes vitamins, and serves many other functions. Yet the microbiome is