Leó Szilárd (Hungarian: Szilárd Leó, February 11, 1898 – May 30, 1964 German: Spitz, Leo until age 2) was a Hungarian- born American physicist and inventor. He conceived the nuclear chain reaction in 1933, patented the idea of a nuclear reactor with Enrico Fermi, and in late 1939 wrote the letter for Albert Einsteins signature that resulted in the Manhattan Project that built the atomic bomb.
