The study of heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) has revealed many, sometimes unexpected, properties of strongly interacting matter under extreme conditions. Systematic surveys of these collisions over a wide range of collision energy and system size have shown convincingly that at sufficiently high energies a dense, interacting medium is formed early on in the collision process. Many qualitative connections between experimental observations and fundamental concepts of the theory of strong interactions, QCD, have been established, including the formation of the initial collision state, the interaction of fast partons with the medium and the dynamics of the expansion of the medium. Still, many important question relating to the nature of the medium and the process of its formation remain to be answered. In this paper, I will discuss selected measurements from RHIC and point out opportunities for measurements in heavy ion collisions at the LHC.

PACS numbers: 24.85.+p, 25.75.Nq