Abstract: In ultra-relativistic collisions of nuclei at the Relativistic Heavy Ion Collider (RHIC) and future Large Hadron Collider (LHC), nuclear matter will be compressed and heated to energy densities reached only within the cores of dense stars and within the first microsecond after the origin of the Universe. At such energy densities nuclear matter "melts" and is predicted to form a plasma of deconfined quarks and gluons. The goal of physicists in this field is to create and uniquely identify the quark-gluon plasma, and to study its properties. In order to accomplish this an understanding of the behavior of the nuclear, hadronic and partonic matter (which exists at various stages of ultra-relativistic collisions) is necessary. A dedicated collider facility (RHIC) including several large detector systems have been constructed at Brookhaven National Laboratory to carry out this task. I will present a motivation for this field of physics and discuss some of the signatures of a quark-gluon plasma. I will focus on the new experiments at RHIC and their anticipated measurements, and mention recent results from heavy ion experiments at CERN, in order to provide a flavor for the present and future physics opportunities of the field.