  After decades of painstaking research, the field of heavy ion physics has
reached an exciting new era. Evidence is mounting that we can create a high
temperature, high density, strongly interacting ``bulk matter'' state in the
laboratory -- perhaps even a quark-gluon plasma. This strongly interacting
matter is likely to provide qualitative new information about the fundamental
strong interaction, described by Quantum Chromodynamics (QCD). These lectures
provide a summary of experimental heavy ion research, with particular emphasis
on recent results from RHIC (Relativistic Heavy Ion Collider) at Brookhaven
National Laboratory. In addition, we will discuss what has been learned so far
and the outstanding puzzles.
