We have used deep 1.4GHz VLA observations of the ECDFS (rms~6 microJy) to study the sub-mJy radio source population. The sub-mJy radio sky is a complex mix of star-forming galaxies and radio quiet AGN, with a declining radio-loud AGN component. We find convincing evidence that the radio emission in radio-quiet AGN is related to star-formation rather than to emission from the central SMBH. These results have important implication for future radio surveys, including those with the SKA. Find here the list of the publications from our group on this topic.