Although the development of the germ theory of disease in the latter half of the nineteenth century marks a major revolution in medical science, comparable to the discoveries of Galileo in astronomy or Darwin in biology, it cannot be reduced to the heroic efforts of a single researcher or group of researchers. Rather, a number of conceptual, technological and institutional preconditions made the germ theory possible. Among these, contagionism, microscopy and hospital medicine all played a major role. The germ theory of disease facilitated a wide range of scientific advances, including the isolation of pathogens, the creation of vaccines and the introduction of antiseptics in surgery.