Some of the new developments in the theory of heavy ion collisions are reviewed. Much of the last progress has been triggered by the high energies available at RHIC. In the near future, the LHC will extend the energy reach in heavy ions by a factor thirty and give access to new QCD regimes characterized by large densities and temperatures and corresponding modified evolution equations.

PACS numbers: 25.75.--q, 25.75.Nq