Gaia, the largest entity in the nested system of life on Earth, is surely not an organism, but it nevertheless shows a kind of physiology with fascinating internal dynamics. This statement implies physiologic functions, chemical cycles, even feedback loops that have some role in long-term stability. What are these functions, how do we know they exist, and how do we learn about them? This is the subject that Tyler Volk tackles brilliantly in Gaia's Body. A seamless, engagingly readable introduction to the budding new field of Earth physiology, Gaia's Body blends real science with evocative imagery in describing the system of life, soil, ocean, and air we have termed the biosphere. Volk shows how every important chemical in the atmosphere is regulated by living processes; why strange, spaghetti-like bacteria off the coast of Chile have an intimate connection with the plants in your backyard; why "biochemical guilds" may be Earth's most important unit of life; and even how scientists have detected the "breathing" of the biosphere. He examines long-term trends in Earth's evolution (is Gaia growing colder? more complex?) and examines humanity's role in Gaia's past and future.