On December 2, 1942, Enrico Fermi and colleagues achieved the first man-made, self-sustaining, controlled nuclear reaction. Their nuclear reactor, an atomic pile called Chicago Pile 1 (CP-1), was a 57-layer lattice of 40,000 graphite blocks enclosing 19,000 pieces of uranium metal and uranium oxide inside a 24-square-food wooden framework. Neutron-absorbing cadmium rods were inserted to control the reaction. In November 2013, the Department of Engergy posted 21 pictures showing the construction of CP-1 and the birth of the atomic age. View them all at magazine.uchicago.edu/inquiry/cp1.