Answer
Leptons are subatomic particles that are not subject to the strong force and that include the electron, muon, and tau particles. They also include the electron neutrino, muon neutrino, and tau neutrino. In 1964, Sheldon Glashow, John Iliopoulos, and Luciano Maiani showed that the leptons are organized into two doublets: one containing the electron and electron neutrino, and the other containing the muon and muon neutrino.