Isn't that the person in a church? No, that's a pastor. Today is about Louis Pasteur; a biologist and chemist from France. Pasteur discovered in 1860 that bacteria can make people sick. The existence of bacteria had been known since 1676, but their effect on other living things was still unclear. It was only after Pasteur's discovery that some food products were first heated to prevent bacteria. This is where 'pasteurisation' comes from! However, Pasteur did and could do much more. For example, he also discovered a vaccine against rabies.