Richard Feynman proposed the parton model in 1969.
The model described hadrons such as protons and neutrons as collections of point-like constituents called partons. Feynman developed it to analyze collisions involving hadrons at extremely high energies, where a fast-moving proton could be treated as if its internal components responded independently during a brief interaction.
The idea became especially important in interpreting deep inelastic scattering, in which electrons or other particles probe the proton’s interior. James Bjorken and Emmanuel Paschos applied the parton picture to electron–proton scattering in work also published in 1969.
A common mix-up is treating “parton” as an entirely separate permanent particle species. Later developments in the quark model and quantum chromodynamics showed that partons correspond to quarks, antiquarks, and gluons, depending on the energy scale and resolution of the observation. The parton model remains a useful high-energy approximation.