Nobel foundation · Public domain

Wolfgang Pauli formulated the exclusion principle — the rule that no two electrons in an atom can occupy the same quantum state — which became a foundation of how physicists understand the structure of matter, and won him the 1945 Nobel Prize in Physics on a nomination from Albert Einstein. Fifteen years earlier, to preserve the conservation of energy in beta decay, he had proposed the existence of a nearly undetectable particle that Enrico Fermi later named the neutrino; it wasn't confirmed to exist until 1956, two years before Pauli's death.