This is perhaps the classic example of a mistake that changed the world for the better. In this case, the world benefited as a result of bad laboratory technique. It was technique at its worst followed by science at its best.

To be able to connect a result with an action or reaction in science you try to eliminate as many outside variables as possible. In chemistry, this means making sure no outside chemical or organic material contaminates your samples. In 1928, Alexander Fleming, an otherwise brilliant scientist, accidentally left a bacteria sample uncovered by an open window. Fleming’s lab was notoriously disorganized, and this was likely not the first time his samples had been contaminated. By the time he had discovered the mistake, which of course should have rendered the sample useless, a number of mold spores had begun to grow in the rich solution in the petri dish. This one happened to be used to grow the deadly staphylococcus bacteria.

There were several ruined samples in petri dishes, but one was different. Fortunately for the world, Fleming took a careful look at the results of his mistake. Upon detailed examination, he saw that one of the molds was doing something no one had ever seen anything do before. It was killing the bacteria near it. Later, he was able to determine that this particular mold grew on, among other things, bread left out too long. Finding the mold in the petri dish led Fleming and his team to create the first antibiotic. This was penicillin, which has since saved tens of millions of lives.

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