  This short paper is an attempt to describe a theorist's view of the goals of
relativistic heavy ion program which has just entered the collider era. These
goals are centered around understanding the properties and the critical
behavior of Quantum Chromo-Dynamics (QCD) in the non-linear regime of high
color field strength and high parton density. Some of the current theoretical
challenges are highlighted, and the place of heavy ion research in the broader
context of modern particle and nuclear physics is discussed.
