Penicillin was discovered by Alexander Fleming in 1928. Fleming was a Scottish scientist interested in bacteriology and immunology. Somewhat by accident, he determined that antibiotic properties could be derived from the Penicillium fungi. In 1945, Fleming won the Nobel Prize for his discovery.
Penicillin was one of the first medicines to fight certain serious bacterial infections successfully. Today, some bacteria have become resistant to penicillin, but the drug is still widely used. There are several different kinds of penicillins, but they all work by killing bacteria or preventing their growth.
Fleming was born in Scotland in 1881 and died in London in 1955.