A French chemist, he debunked the then widely held theory of spontaneous generation.
Emperor Napoleon III asked Pasteur to investigate spoilage of wine which were causing considerable economic losses in the wine industry. Pasteur went to a vineyard in Arbois in 1864 to study this problem. He demonstrated that wine diseases are caused by microorganisms that can be killed by heating the wine to 55deg.C for several minutes. Applied to beer and milk, this process, called "pasteurization", soon came into use throughout the world.
His experimentation with fermentation led him to the germ theory, which he then applied to contagious disease, laying the foundation of modern microbiology and biochemistry. He later contributed to the development of the early vaccines for rabies and immunisation.