In 1928, Alexander Fleming returned from vacation and accidentally discovered penicillin, the medical breakthrough that became the world's most widely used antibiotic

In 1928, Scottish scientist Sir Alexander Fleming returned to his laboratory after a two-week vacation. An accidentally contaminated Petri dish that most researchers would have thrown away without a second thought was waiting for him.

But Sir Alexander Fleming decided to take a closer look and his research led to the discovery of penicillin, the world's first true antibiotic—a breakthrough that has saved millions of lives and transformed modern medicine.