Prepare to set aside what you think you know about yourself and microbes. Good health--for people and for plants--depends on Earth's smallest creatures. The Hidden Half of Nature tells the story of our tangled relationship with microbes and their potential to revolutionize agriculture and medicine, from garden to gut.

When David R. Montgomery and Anne Bikle decide to restore life into their barren yard by creating a garden, dead dirt threatens their dream. As a cure, they feed their soil a steady diet of organic matter. The results impress them. In short order, the...