Constructed of a lattice of graphite blocks full of uranium oxide and uranium metal that were stacked 57 layers high, Chicago Pile-1 bore little resemblance to today's nuclear reactors [source: Alfred]. A three-person "suicide squad" was waiting to step in and shut the reactor down in case the reactor's safety features failed. Fortunately, the more than 50 people in attendance that day were able to share a collective sigh of relief -- as the squad was not needed [source: Alfred]. The reactor worked without a hitch, and the nuclear era was born.

In 2011, more than 440 nuclear power plants in 30 countries across the globe were busy supplying 14 percent of the world's current electricity needs [source: World Nuclear Association].