From the first bacterial 'germ of life' cells that formed in the hot, hostile, and highly volcanic Earth nearly 4 billion years ago, to the present day, life has been an unbroken continuum. Bacterial cells have been the building blocks from which higher living things, including humans, are constructed. The biochemical pathways and metabolic processes that bacteria evolved and perfected still give life to the DNA of all living matter. By definition, the thin outer layer of our planet, the biospherethat is metabolizing as a result of the life it containsis alive. The essential role of microbes in maintaining the living Earth did not cease or diminish with the coming of visible living organisms. Only recently has it been recognized to just what extent invisible life controls the planet. We need to acknowledge the symbiotic nature of the biosphere, where microbes represent more than half of the living matter; the interconnections between all living things and the environment; and the dan