While the study of QGP now transitions to the Large Hadron Collider at CERN, RHIC’s facilities will undergo a major transformation to become the new Electron-Ion Collider. This next-generation machine will probe the internal structure of protons and nuclei, building on the knowledge gained at RHIC. Throughout RHIC’s history, the Relativistic Nuclear Collisions (RNC) group of the Nuclear Science Division (NSD) at Lawrence Berkeley National Laboratory (LBL) played a crucial role, making significant contributions to the STAR and sPHENIX experiments that were essential for these discoveries. Their work in developing detectors and analysis techniques was pivotal in unraveling the mysteries of the QGP. RNC is taking on similar roles in developing the detectors and the physics program for the future ePIC experiment at the EIC.