World's first antibiotic
Alexander Fleming, a Scottish doctor working in England, discovered the antibiotic penicillin in 1928. His discovery was partially accidental.
Fleming was a research scientist studying the Staphylococcus bacteria. When he went for a fortnight's holiday, he left his lab in a mess. When he returned, the bacteria had covered his slides - except for a clean bit next to a patch of fungus.
Fleming believed the fungus had released a substance that killed off the bacteria. He studied the slide and named the bacteria-killing substance penicillin.
Producing more penicillin proved difficult. It took Australian scientist Howard Florey and British biochemist Ernst Boris Chain almost 10 years to develop a method that created enough of the drug.
But when the antibiotic became available in 1941, tests showed penicillin cured lots of serious bacterial infections within days. Penicillin became the world's first superdrug.
In 1945, after penicillin saved thousands of lives in the second world war, Fleming and his colleagues Florey and Chain were awarded the Nobel Prize for Medicine.