Few figures dominated 19th century science as Louis Pasteur did. Pasteur (1822-1895) developed key understandings in chemistry, biology, and medicine. A chemist, he showed the asymmetric nature of certain crystals. From his work on crystallography, he moved on to the chemistry of fermentation, and demonstrated that fermentation is a chemical process carried out by tiny organisms. His findings in fermentation led him to debunk the myth of spontaneous generation and to propose methods for preventing the growth of bacteria in food items.
Pasteur was the first scientist to artificially attenuate viruses for use in vaccines. He created several veterinary vaccines before his development of the rabies vaccine in 1885 for use in humans.
Today, Pasteur plays the role of national hero in France, and the Pasteur Institutes he founded continue to develop breakthroughs in the prevention and treatment of infectious disease.