  The presence of non-thermal components in galaxy clusters is now clearly
established. Diffuse radio emission from the Intra Cluster Medium (ICM) of
several galaxy clusters is revealed in the form of radio halos and relics.
These emissions are synchrotron radiation from a population of relativistic
electrons mixed with the thermal gas and diffusing through microGauss turbulent
magnetic fields. Radio Halos are surely the most interesting evidences of
cluster non-thermal activity and understanding their origin is one of the most
intriguing problems of the physics of the ICM. I review observational and
theoretical results obtained in the last few years and discuss the impact of
present (e.g. GMRT) and future low frequency radio telescopes (LOFAR, LWA) in
our understanding of non-thermal phenomena in galaxy clusters.
