Louis Pasteur was a French biologist and chemist who revolutionized medicine and public health through his discoveries. He developed vaccines for rabies and anthrax, and pasteurization to stop bacterial contamination of foods and drinks. Pasteur's life work can be divided into three parts - studying crystallography and fermentation early in his career, then developing methods for sterilization and rescuing industries from disease. In his final years, he established microbiology and the science of immunology, developing the first vaccine for rabies. Pasteur is considered one of the greatest biologists of all time for his many scientific breakthroughs that have saved countless human lives.