Penicillin was discovered by Alexander Fleming in 1928 at St. Mary's Hospital in London. He found that a mold called Penicillium notatum (now known as Penicillium rubens) produced a substance that killed bacteria, which he named penicillin

. Fleming's discovery marked the beginning of the antibiotic era, as penicillin was the first true antibiotic effective against many bacterial infections

. Although Fleming discovered penicillin, he did not have the resources to purify and mass-produce it. This crucial development was carried out in the late 1930s and early 1940s by a team of scientists at the University of Oxford led by Howard Florey, along with Ernst Chain and Norman Heatley. They developed methods to isolate, purify, and produce penicillin on a large scale, making it a practical and life-saving drug

. For their combined efforts in the discovery and development of penicillin, Fleming, Florey, and Chain were awarded the Nobel Prize in Physiology or Medicine in 1945