💊 Penicillin (antibiotics)

📰 Halfway through an experiment with bacteria in 1928, Alexander Fleming went on vacation. He left a dirty petri dish in the lab sink and when he got back, he found bacteria had grown all over the plate, except in an area where mold had formed. Penicillin was discovered.

ℹ️ Source: https://www.rd.com/funny-stuff/10-accidental-discoveries-put-to-good-use/