Answer
Deep Inelastic Scattering (DIS) experiments provided crucial evidence for the existence of quarks. In DIS, a beam of high-energy electrons is directed at a target, such as a proton. If the proton were simply a point-like particle, the electrons would scatter elastically without any significant energy loss. However, the observed scattering patterns indicated that the proton had an internal structure, with point-like constituents called partons.