Alexander Fleming discovered penicillin in 1928 while studying influenza at St. Mary's Hospital in London. He noticed that a mold had developed on a culture of staphylococci bacteria plates and created a bacteria-free circle around itself. Fleming experimented further and named the active substance penicillin. This discovery of antibiotics in mold led to the development of modern antibiotics and significantly increased lifespans in the 20th century. Fleming shared the 1945 Nobel Prize in Medicine with Florey and Chain for his role in the discovery of penicillin.