197 years ago, on 27 December, Loui Pasteur was born. He is well known for his discoveries of the microbial fermentation and pasteurization. But he also made important contributions to chemistry. Through his studies on tartaric acid, he found that its crystals had two different structures, which were mirror images. They were identical in physical and chemical properties, and different in only optical rotation. Today, these structures are called enantiomer. Pasteur, who showed the existence of chirality, is now recognized as the founder of stereochemistry.