The Fermi era refers to the era of research and experimentation led by Italian physicist Enrico Fermi, who made significant contributions to nuclear physics, particle physics, and quantum mechanics during the early to mid 20th century. Fermi is best known for his work on the development of the first nuclear reactor and his pioneering research on beta decay and high-energy particle physics. The Fermi era also saw advancements in the understanding of neutrinos, cosmic rays, and the behavior of elementary particles, laying the foundation for modern particle physics.