The Germ Theory of Disease

In the mid-1800s, the French chemist Louis Pasteur was examining the fermentation process of alcohol. Wine was spoiling very quickly which caused great economic loss, so Pasteur was called upon to solve the problems in the French wine industry. While looking at wine under a microscope, he discovered that fermentation was caused by little microscopic organisms that were producing lactic acid. He named the cells bacteria. He experimented more and soon developed the process of pasteurization, which kills germs in liquids (such as milk) by using heat. When Pasteur heated the wine at about 120 degrees, the lactic acid producing bacteria was killed.  It was also discovered that bacteria causes illness. This process killed germs which prevented sickness for people during that time as well as today.

Milk going through the pasteurization process