Chemotherapy – the invaluable treatment that has saved countless lives of cancer patients through blocking different functions in cell growth and replication – stemmed from the discovery, during World War II, that exposure to mustard gas in conflict significantly reduced soldiers’ white blood cell count, sometimes fatally. The compound nitrogen mustard was studied further by researchers and found to halt the growth of rapidly dividing cells such as cancer cells. This is just one example of humankind adapting a negative discovery into a positive one.