French scientist Louis Pasteur has been called the founder of modern medicine. He proved that germs spread disease, and his work has saved millions of lives. A university chemistry professor, Pasteur is best known for discovering pasteurization, a process by which bacteria and molds are killed when liquids are heated. The process was named for him and is used today.French scientist Louis Pasteur has been called the founder of modern medicine. He proved that germs spread disease, and his work has saved millions of lives. A university chemistry professor, Pasteur is best known for discovering pasteurization, a process by which bacteria and molds are killed when liquids are heated. The process was named for him and is used today.