Discovery of Penicillin
Alexander Fleming discovered penicillin, leading to the development of antibiotics that would save millions of lives.
On September 28, 1928, Scottish bacteriologist Alexander Fleming noticed that a mold colony (Penicillium notatum) had contaminated a petri dish of Staphylococcus bacteria and was killing the surrounding bacterial colonies. This accidental discovery led to the development of penicillin, the world's first widely used antibiotic. Mass production during World War II saved countless lives, and antibiotics have since prevented hundreds of millions of deaths from bacterial infections.