A cup of seawater contains 100 million cells, which are preyed upon by billions of viruses. Fifty million tons of fungal spores are released into the atmosphere every year. And the human gut is home to somewhere between 500 and 1,000 species of bacteria. The more we learn about microbial biodiversity, the clearer it becomes that the vast majority of life has long gone unseen, and unobserved. The flowering of microbial science is revolutionizing biology...