In high-energy nucleus-nucleus collisions, physicists are able to study the trillion-degree soup of quarks and gluons, known as the quark-gluon plasma (QGP), that existed in the very early universe. The Large Hadron Collider (LHC) at CERN has opened a new frontier for investigating some unique properties of this strongly-interacting QGP matter including the suppression of hard probes (jets, heavy quarks) and behavior as a ‘nearly-perfect’ fluid. I will first review key findings of heavy ion program by the Compact Muon Solenoid (CMS) experiment in the early phase of the LHC program. The CMS experiment is preparing an extensive Phase-2 upgrade program to meet the more challenging condition of the high-luminosity LHC (HL-LHC) and bring new capabilities to the detector. I will then present our efforts on realizing the most comprehensive QGP detector ever built at CMS by 2030s and discuss how it will address unique key questions and open exciting new opportunities.
