Discusses the current scientific knowledge of the subterranean world, following the progress of discovery from Charles Darwin's experiments with earthworms, to Lewis and Clark's first encounter with prairie dogs, to the use of new genetic tools that are revealing an astonishingly rich ecosystem beneath our feet. As Wolfe explains, creatures of the soil can work for us, by providing important pharmaceuticals and recycling the essential elements of life, or against us, by spreading disease and contributing to global climate change. The future of our species may well depend on how we manage our living soil resources.