The document provides a summary of the accidental discovery of penicillin by Dr. Alexander Fleming in 1929 at St. Mary's Hospital in London. While experimenting with bacteria cultures, Fleming noticed a fungus in one of his culture plates was preventing the growth of surrounding bacteria. Further testing showed that even when highly diluted, extracts from the fungus could kill bacteria. Although Fleming had discovered penicillin's antibacterial properties, he did not identify the fungus and lacked knowledge of fungi. It would take years of further work before penicillin's potential was realized.