The Accidental Revolution

In 1928, Alexander Fleming returned from vacation to find mold growing on a Petri dish of Staphylococcus bacteria. The bacteria near the mold were dead. The mold was Penicillium notatum, and it was secreting a chemical that killed bacteria.

It took another decade before Howard Florey and Ernst Boris Chain figured out how to purify and mass-produce penicillin. By 1944, it was saving thousands of soldiers' lives in World War II. Before antibiotics, a simple scratch could lead to a fatal infection.