Louis Pasteur

Born in Dole, France, in 1822, Louis Pasteur trained as a chemist before making discoveries that reshaped biology and medicine. He became famous for showing that tiny living organisms are involved in fermentation and spoilage, helping overturn the idea of spontaneous generation.

Pasteur's research led to practical breakthroughs as well as big scientific ideas. He developed pasteurization to help prevent contamination in foods and drinks, and he created vaccines for diseases including anthrax and rabies. His work helped lay the foundations of germ theory and modern microbiology.

He spent much of his career in Paris and became one of the most celebrated scientists of the 19th century. Pasteur died in 1895, but his influence remains enormous in medicine, public health, and the history of science.