In recent years many efforts have been devoted to the search for the Quark Gluon Plasma, a new, deconfined phase of hadronic matter, through ultrarelativistic heavy ion collisions. In 1986 the Alternate Gradient Synchrotron in Brookhaven started accelerating nuclei, thus beginning the Era of high energy nucleus-nucleus collisions. Since then, many experiments developed, with increasing luminosity and energy of the ion beams: the Large Hadron Collider, expected to be completed by 2007 at CERN will allow to study Pb-Pb collisions at y/s ~ TeV/nucleon
