On this date in 1942, Enrico Fermi and his team of scientists begin construction of the world’s first primitive nuclear reactor—in an abandoned squash court under the west stands of Stagg Field. Over the next 15 days, two crews work day and night in 12-hour shifts to construct the 20-foot beehive-shaped structure of wood, graphite and uranium known as Chicago Pile-1. It would create the first controlled, self-sustaining nuclear chain reaction on Dec. 2, 1942. #nuclear75