When Alexander Fleming, a brilliant but sometimes careless scientist, returned to his lab after a summer holiday, in 1928, he found his work ruined. The bacteria cultures he had been growing were contaminated by fungus. As it grew, it killed all the colonies it touched.
Most people would have simply started over, but Fleming switched his focus from the bacteria to the fungus itself. He identified the mold and the bacteria-killing substance, which he called “penicillin.” Seemingly in a single stroke, Fleming had created the field of antibiotics