Enrico Fermi, Italian-born American nuclear physicist.

Enrico Fermi, Italian-born American nuclear physicist. Fermi (1901-1954) constructed the first working nuclear reactor, in a squash court at the University of Chicago in 1942. He won the Nobel prize for physics in 1938 for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons. (Photo by Oxford Science Archive/Print Collector/Getty Images)