  FERMI (formely GLAST) and LOFAR will shortly provide crucial information on
the non-thermal components (relativistic particles and magnetic field) in
galaxy clusters. After discussing observational facts that already put
constraints on the properties and origin of non-thermal components, I will
report on the emission spectrum from galaxy clusters as expected in the context
of general calculations in which relativistic particles (protons and secondary
electrons due to proton-proton collisions) interact with MHD turbulence
generated in the cluster volume during cluster-cluster mergers. In this
scenario (known as re-acceleration scenario) diffuse cluster-scale radio
emission is produced in massive clusters during merging events, while gamma ray
emission, at some level, is expected to be common in clusters. Expectations of
interest for LOFAR and FERMI are also briefly discussed.
