Glenn Seaborg was a 26-year-old chemistry instructor at the University of California Berkeley when he heard the news in January 1939: German scientists had split the uranium atom. With the world on the brink of war, thoughts immediately turned to harnessing nuclear fission to create an atomic bomb. Using Cal’s cyclotron to bombard uranium with neutrons, Seaborg created a new element — plutonium — that promised to be an even better fuel for a bomb. When the Japanese attack on Pearl Harbor plunged America into war, Seaborg joined the Manhattan Project at the University of Chicago, where he would play a key role in creating the plutonium for the bomb that leveled the city of Nagasaki. Only then could Seaborg publicly reveal his discovery of the element that had ended the war.