The X-Men are a superhero team in the Marvel Comics Universe. Under a cloud of increasing anti-mutant sentiment, Professor Xavier created a haven at his Westchester mansion to train young mutants to use their powers for the benefit of humanity, and to prove mutants can be heroes. Xavier recruited Cyclops, Iceman, Angel, Beast and Jean Grey, calling them "X-Men" because they possess special powers due to their possession of the "X-Gene", a gene normal humans lack but which gives Mutants their abilities. Early on, however, the "X" in X-Men stood for "extra" power which normal humans lacked. It was alluded to that the mutations were incurred as a result of radiation exposure. All five original X-Men, including Professor Xavier were stated to be the children of parents who worked on atomic weapons for the United States military.