High Energy QCD from RHIC to the EIC

The Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) is nearing the completion of its data collection phase. RHIC has facilitated collisions of various nuclear beams, including proton-proton and proton-nucleus collisions, utilizing spin-polarized protons. This presentation will outline the extensive cold QCD results obtained from the RHIC experiments STAR and PHENIX, as well as future opportunities including the new sPHENIX experiment. Over the past decades, RHIC experiments, along with fixed-target experiments involving nuclear and lepton spin polarization, have significantly advanced our understanding of nucleon spin and 3D structure, and QCD effects in cold nuclear matter. The current experimental insights and understanding of nucleon spin and structure will be put in context with the anticipated data from the future Electron-Ion Collider (EIC) at BNL, which will explore electron-proton and electron-nucleus collisions including nuclear and lepton polarization.