Biography: Through his experiments with bacteria in the 1860s, French chemist Louis Pasteur disproved the centuries-old belief that disease was caused by spontaneous generation, the idea that disease-causing parasites arise spontaneously in an organism. Pasteur demonstrated that the fermentation of wine to vinegar was caused by living agents that entered the wine from the air surrounding it, proving instead that microorganisms were able to reproduce. Drawing the conclusion that airborne agents could enter the bodies of humans and animals and cause disease, he then devoted his research to isolating the organisms that cause specific diseases and finding treatments to prevent them. He developed vaccines for anthrax, chicken cholera, and rabies. Pasteur's germ theory of disease was not immediately accepted, but thanks to the work of other pioneering scientists, such as Robert Koch, it eventually provided the foundation for modern branches of medicine such as microbiology, bacteriology, virology, and immunology. Pasteur is also known for developing pasteurization (originally for wine), a process of heating and rapidly cooling liquids that is used to kill disease-causing bacteria, particularly in dairy products.