generation of low-frequency radio arrays, including the Giant Metrewave Radio Telescope (GMRT), the LOw Frequency ARray for radio astronomy (LOFAR), the Murchison Widefield Array (MWA) and the Long Wavelength Array (LWA), will improve the current observational situation in the near future.

In the recent past, claims of hard X-ray emission from nearby cluster of galaxies have been reported [@hardxray]. One possibility is that this X-ray emission originates from the inverse Compton (IC) scattering off background radiation of the same non-thermal high energy electron population responsible for the radio emission. Most of the clusters reportedly detected at hard X-ray frequencies are merging clusters [@nevalainen2004], and the detections themselves are still debated [@rossetti04; @Ajello:2008rd]. In addition, it is unclear if simple models for the non-thermal population fueling radio and hard X-ray emissions can self-consistently explain data from clusters (see e.g. the case of new radio data from the Ophiuchus cluster of galaxies [@ophradio] in connection with the recent claim of a non-thermal hard X-ray detection with INTEGRAL [@ophhxr]). Future hard X-ray missions, including the Nuclear Spectroscopic Telescope Array (NuSTAR) [@nustar] and the International X-ray Observatory (IMX) [@syx], will play a key role in settling the mentioned controversies, as well as in fostering 