Quark-Gluon Plasma and Hadron Physics

While the quarks are the elementary constituents of matter, they are con.ned inside a hadron and never found in isolation. However, at high temperature and density, the quarks will be liber ated from the hadrons to from a Quark-Gluon Plasma through a decon.ning phase transition in Quantum Chromodynamics (QCD). To probe such a phase transition and the properties of Quark-Gluon plasma, which is also believed to have existed miliseconds after the Big Bang, relativistic heavy ion experiments have been performed at RHIC BNL and planned at LHC. In this talk, I will survey this new .eld, summarize the .ndings so far and comment on future expectations. The prospects of reviving hadronic physics at future heavy ion collision experiments are also discussed.