Enrico Fermi's study was focused on the ATOM. He was an Italian physicist who won the Nobel Prize in Physics in 1938 for his work on induced radioactivity. He is best known for his work on the development of the first nuclear reactor, which he used to create the first controlled nuclear chain reaction. He also studied the structure of the ATOM and developed the theory of beta decay. His research helped to lay the foundation for the development of nuclear energy.