The worldâs first collisions between two beams of protons occur in the Intersecting Storage Rings (ISR). During its 13 years of service, the ISR makes important contributions to the understanding of the constituents of the proton and probes the strong nuclear force that links binds quarks and gluons together inside protons and neutrons. It also becomes the first proton-antiproton collider and the first ion collider, enabling CERN to gain unique expertise for its subsequent particle collider projects.