Enrico Fernando Fermi (September 29, 1901 — November 28, 1954) was an Italian-American physicist who worked on the first nuclear reactor and helped make quantum theory. He also was important to particle physics, and statistical mechanics. Fermi won the Nobel Prize in Physics in 1938 for his work on induced radioactivity. He built the world's first nuclear reactor. Fermi was one of the greatest scientists of the 20th century.