Enrico Fermi (1901-1954), Italian-American physicist. Fermi carried out fundamental theoretical and experimental work on nuclear and quantum physics and is best known for building the first nuclear reactor. In the 1930s he established the theory of beta decay and discovered the statistical laws obeyed by such elementary particles as the electron. Fermi won the 1938 Nobel Prize in Physics for his work on using neutrons to initiate nuclear reactions. His research at Chicago University into ways of producing a self-controlled, self-sustaining nuclear fission reaction led, in 1942, to the construction of the first atomic pile i.e., nuclear reactor, thus beginning the age of nuclear power. A year later, at Los Alamos, he worked on the Manhattan Project developing the atomic bomb.