  Towards the end of 2010, some 25 years after the very first collisions of
ultra-relativistic heavy ions at fixed target energies, and some 10 years after
the start of operation of the Relativistic Heavy Ion Collider (RHIC), the LHC
opened a new era in heavy ion physics with lead on lead collisions at
$\sqrt{s_{NN}} = 2.76$ TeV. After a short reminder of the main results from
lower energies, this review highlights a few selected areas where significant
progress has been made during the first three years of ion operation at the
LHC.
