Penicillin was discovered by accident when Fleming left a culture of staphylococcus germs uncovered for a few days. He noticed that an unknown mold killed the staphylococcus bacteria. Upon further study, he found that this mold did not affect Human cells. Although it took over a decade for further development, this antibiotic revolutionized medicine.
A visual chronology of Asimov's ~1500 scientific inventions and discoveries.
