Louis Pasteur famously said, "In the fields of observation chance favors only the prepared mind." Pasteur brought to the study of chemistry, microbiology, and applied immunology, a mind open, innovative, and insightful. Born of peasant stock in the French Jura, he worked with dogged determination all his life and often in the face of strenuous opposition. Through an unbroken succession of rigorously designed and meticulously performed experiments, Pasteur developed veterinary vaccines and halted grievous losses in the French wine, silk, and dairy industries. He provided the crucial experimental support for the germ theory of disease which enabled Joseph Lister and others to prevent infections in surgical patients and in new mothers. During the development of the vaccine against rabies, Pasteur and his colleagues often risked their own lives, but they delivered humankind from the terror of this agonizing and almost always fatal illness.