In 1928, Alexander Fleming was studying the bacterium, Staphylococcus, when some of the bacteria became contaminated with Penicillium fungus and stopped growing. Fleming decided that some chemical produced by the Penicillium fungus must be stopping the growth of the Staphylococcus bacteria. Fleming isolated that chemical and called it “penicillin.” Fleming’s own attempts to treat patients with penicillin were not very successful, but during the next few decades, scientists were able to isolate purer doses of penicillin and the new drug turned out to be one of the most significant medical advances of the twentieth century. Since antibiotics kill living cells, one of the problems is finding antibiotics that will kill bacteria cells without killing the patient’s own cells. But that’s our topic for next time.