Never one to worry about neatness, Scottish-born scientist Alexander Fleming often grew cultures in unwashed petri dishes. In the hot summer of 1928, Fleming left for a two-week vacation. He left his London laboratory a mess and didn't close his window. In his haste, he also forgot to clean up an old culture plate that he had smeared with staphylococcus bacteria. Soon after he left, a spore containing a rare strain of a fungus mold called penicillium drifted into his lab from another lab in the same building. By chance, it settled onto the messy culture plate.
And if that wasn't lucky enough, the weather stepped in to add even more. The temperature briefly dropped, so the mold began to grow. Then things heated up again, and the bacteria on the plate sprouted like a weed. Except in one spot. That one spot attracted Fleming's eye when he returned from vacation. It was where the penicillium spore had settled and grown. Fleming believed he had discovered something very important. Not everyone else agreed. In fact, it would take until World War II, when he was well into middle age, before anyone appreciated his discovery.
