Microbes are the oldest and most diverse group of living organisms on the planet. Microbes include bacteria, viruses, protozoa, algae, yeasts, and molds. In most parts of the world, microbes are a major cause of morbidity and mortality, killing tens of millions of people per year. Newly emerging diseases, like MERS and Ebola, and the acquisition of drug resistance by some ancient enemies make vigilance the eternal price of health. Unquestionably, microbes promise to play an important role in our lives.