Alexander Fleming's 1928 discovery of penicillin is one of medical history's most famous moments. But the original wonder drug languished in laboratories until a World War II research program that rivaled the Manhattan Project-at times literally-brought it to hospitals and battlefields.

By the summer of 1941, Oxford University researchers led by Howard Florey and Ernst Chain had shown that penicillin could cure people of deadly bacterial infections. But making the drug was difficult: The Oxford group started out growing the antibiotic-producing Penicillium mold in bedpans, and even resorted to collecting penicillin from treated patients' urine. Still, they amassed enough of the drug to treat only six patients. With bombs falling on Britain, Florey and a collaborator went to the United States for help.