Understanding how the first active galaxies (AGN) and quasars formed in the early Universe and how they evolved along Cosmic Time is a major observational and theoretical effort. Despite the progress made in recent years, often sparse and not always conclusive, we do not yet have a clear consistent picture of when did SuperMassive Black Holes start to accrete, which growth modes occur, and under what conditions. What is required is a systematic analysis and interpretation of high-quality multi-wavelength data on a sample as large as possible of representative AGNs. I will exploit X-ray, optical, infrared and millimeter data from different multi-wavelength survey I am already involved in and foresee an efficient and timely use of newly inaugurated facilities such, as ALMA, X-Shooter, WFC3, LUCIFER among others. With these data I will construct the largest, homogeneous and complete sample of AGN to date, needed to address the main objectives of this proposal: 1) determine the AGN bolometric luminosity function, and study its evolution with the cosmic time; 2) measure the incidence of mergers and smooth processes for the triggering AGNs; 3) study the effect of AGN feedback on galaxy growth; 4) provide the first significant samples of high-z AGN to be used as constraints on BH formation models; 5) define optimal strategies to exploit synergies between two upcoming all-sky surveys, eROSITA and Euclid.My previous, recognized experience in the field assures a timely accomplishment of the project. I will be enrolled as a permanent researcher at the Astronomy Department of the University of Bologna - the Host Institute selected for this project. With the additional funding provided by the CIG I will be able to promote my own research activities in addition to my teaching duties. By enhancing my skills in project managements and securing fundings the CIG grant will enhance the possibilities of a quick access to the Associate Professor level.