Penicillin was discovered accidentally in 1928 by Alexander Fleming, a Scottish physician and bacteriologist working at St. Mary's Hospital in London. Fleming returned from a holiday to find that a Petri dish containing Staphylococcus bacteria had been contaminated by a mold (Penicillium notatum). Around the mold, bacterial growth was inhibited, indicating that the mold secreted a substance capable of killing bacteria. Fleming identified and named this substance penicillin. Although he published his findings in 1929, the importance of penicillin was initially overlooked, and it was not until over a decade later that scientists Howard Florey, Ernst Chain, and their team at Oxford developed methods to purify, produce, and clinically test penicillin. Their work led to the mass production of penicillin, which became a crucial antibiotic during World War II, saving thousands of lives.