Experimental overview of heavy-ion physics at the SPS and RHIC

QCD predicts that at a certain critical temperature of the order of Lambda /sub QCD/, strongly interacting matter undergoes a phase transition from the colour singlet hadronic state to a deconfined plasma of quarks and gluons. This review summarizes experimental observables that support the evidence that a new state of matter with properties as predicted for the QGP was observed at the CERN SPS as well as novel experimental probes accessible at the RHIC heavy-ion collider at BNL. (75 refs).