AbstractOver the last few years, the existence of mutual feedback effects between accreting supermassive black holes powering AGN and star formation in their host galaxies has become evident. This means that the formation and the evolution of AGN and galaxies should be considered as one and the same problem. As a consequence, the search for, and the characterization of the evolutionary and physical properties of AGN over a large redshift interval is a key topic of present research in the field of observational cosmology. Significant advances have been obtained in the last ten years thanks to the sizable number of XMM–Newton and Chandra surveys, complemented by multiwavelength follow-up programs. I will present some of the recent results and the ongoing efforts (mostly from the COSMOS and CDFS surveys) aimed at obtaining a complete census of accreting black holes in the universe, and a characterization of the properties of the host galaxies.