We are one with our ever-changing micro-biome and it is us. This book is a thorough and very readable presentation by a science journalist of the latest research on the integrated ecosystems created by bacteria and their hosts. Those expecting to read mostly about the human biome and its effect on our health will be disappointed as the book ranges across the taxonomic “tree of life" in depicting the symbiotic relationships that exist between bacteria and plants, animals, fungi, viruses and other bacteria. In fact, humans, animals, plants, etc cannot live without bacteria and vice versa, and I was left wondering whether we exist to keep bacteria alive! There are a couple of chapters on the human biome where we learn that what types of bacteria exist in our gut can influence the state of our health and the efficacy of drugs on our bodies. Biodiversity is generally good, which is why overuse of antibiotics can be harmful by causing imbalances and eliminating some species. In the future, we may take specific bacterial infusions to cure us of disease or enhance the effect of a drug. But our integrated ecosystem is complex and we still don’t know enough about how to nurture or manipulate it. This was a fascinating read and recommended as a top book by The Economist in 2016.