The Relativistic Nuclear Collisions (RNC) program in the Nuclear Science Division at LBNL carries out experimental research in High Energy Nuclear Physics to elucidate the fundamental nature of Quantum Chromo-dynamics (QCD), which governs the behavior of the basic constituents of matter, quarks and gluons. This program involves probing the structure and interactions of these fundamental constituents both ordinary matter (protons, neutrons, and nuclei) and in dense, energetic states of matter associated with the early universe. In addition to carrying out experiments and analyzing data to address these fundamental questions about the nature of matter, we also develop the detectors and computational approaches needed to drive this program of cutting-edge research. Members of the RNC program play leading roles in the STAR and sPHENIX collaborations at RHIC, the ALICE experiment at CERN, measurements at Jefferson Lab, and are working towards completion of the ePIC detector for the future Electron-Ion Collider.