Louis Pasteur was a French scientist who discovered that tiny, invisible germs cause many diseases, a huge breakthrough for medicine and public health. He invented pasteurization, the heating process that makes milk and other foods safer to drink and eat. He developed vaccines against anthrax and rabies, and in 1885 famously used his rabies vaccine to save the life of a 9-year-old boy who had been bitten by a rabid dog, one of the first successful uses of a vaccine to treat a person after exposure to a deadly disease.