Louis Pasteur was one of the greatest scientists of all time. Pasteur made very important discoveries in biology and chemistry, and the techniques he developed helped greatly to develop medical science and the agricultural and food industries. Pasteur was born in a small town in France during the year 1822. When he was a young man, Pasteur studied science at a university in the city of Paris. He soon did some excellent work in chemistry, and later began his famous study of germs. Pasteur was one of the first scientists to understand that many diseases could be caused by extremely small, invisible organisms. Only a few other scientists had believed this before Pasteur. He advised doctors to wash their hands thoroughly before treating patients. Pasteur also demonstrated that life forms did not arise spontaneously. His research confirmed the idea, developed by previous scientists, that a living organism would not appear unless other individuals of its kind were present. One of Pasteur's most important contributions was a technique that has been named after him: pasteurization. Pasteurization kills the germs that are found in drinks such as milk or beer. Because of Pasteur's technique, people are no longer infected with diseases by drinking these liquids. Just as important as pasteurization was a technique called immunization. Pasteur found that a person or animal could be made safe, or immune, from a disease, by injecting the person with some weakened germs that cause the disease. The body can resist the disease after being immunized in this way. Today, many diseases are prevented by the use of this technique. Pasteur's discoveries also helped to save people who had already been infected with diseases. One such disease is rabies. Rabies is a disease that sometimes occurs in animals. This disease usually kills the animal, but before dying, the animal becomes very aggressive, and may spread the disease by biting a person or another animal. One day, the parents of a young boy came to Pasteur. Their son had been bitten by a dog that had the rabies disease. The parents knew that their son would die from the disease, unless something could be done to save him. Pasteur agreed to help the boy, and the immunization technique saved the boy's life. Pasteur died in 1895. He was greatly admired around the world for his achievements, which have helped all of humankind. Today, Pasteur is considered to be the greatest figure in the history of medicine.