  The Intra-Cluster Medium (ICM) is a rarefied, hot, highly ionized, metal
rich, weakly magnetized plasma. In these proceeding, after having reviewed some
basic ICM properties, I discuss recent results obtained with the BeppoSAX,
XMM-Newton and Chandra satellites. These results are summarized in the
following five points. 1) Currently available hard X-ray data does not allow us
to constrain B fields in radio halos, the advent of hard X-ray telescopes in a
few years may change the situation substantially. 2) There is mounting evidence
that temperature profiles of clusters at large radii decline; however
investigation of the outermost regions will have to await a new generation of
yet unplanned but technologically feasible experiments. 3) The ICM is polluted
with metals, the enrichment has probably occurred early on in the cluster's
life. The abundance excess observed at the center of CC clusters is due to the
giant elliptical always found in these systems. 4) Chandra and XMM-Newton
observations of relaxed clusters have falsified the previously accepted cooling
flow model, heating mechanisms that may offset the cooling are actively being
sought. 5) The superb angular resolution of Chandra is allowing us to trace a
previously unknown phenomenon intimately related to the formation of galaxy
clusters and of their cores.

Astrophysics