Few people change how the world thinks, but Louis Pasteur, born in 1822 in Dole, France, did exactly that. He is remembered for showing that germs cause many diseases.
Pasteur was careful. He designed experiments with special flasks to prove where germs came from.
In 1856, Pasteur began studying why wine and milk spoiled. Then, in 1862, Pasteur tested a heating method, later called pasteurization, to kill harmful germs.
Then, in 1881, Pasteur showed that a vaccine could protect sheep from a disease called anthrax. In 1885, Pasteur successfully treated a boy bitten by a dog with rabies. (Vaccine: a substance that trains the body to fight a disease.)
Pasteur died in 1895. Milk is still heated to kill germs using the method named after him.