Louis Pasteur was a French chemist and microbiologist who made groundbreaking discoveries in vaccinations, microbial fermentation and pasteurization. He developed the germ theory of disease which led him to find the first vaccines for rabies and anthrax. Pasteur also invented the process of pasteurization to stop bacterial contamination in milk, beer, and wine, extending their shelf life. His work proved that microorganisms living in the air, water, soil, and bodies of animals and humans cause disease.