"Understanding the processes regulating galaxy formation is a major open issue in observational cosmology. We now have a fairly detailed census of the diverse high-z galaxy populations, hence time is ripe for fundamental advances in understanding galaxy formation and evolution in the crucial first few billion years. This requires to observationally constrain and clarify the physical processes that operated at those early epochs. Thanks to a new galaxy selection technique that I recently introduced, I have been leading research projects that have now provided major new results on high redshift z~2 galaxies. These include molecular gas first seen in typical high-z galaxies; the major phase of star formation at very high rates; widespread presence of previously unknown Compton-thick AGNs inside massive galaxies; and the existence of evolved galaxy clusters containing X-ray emitting gas already at z~2. Building on the legacy of these discoveries and critical results, I ask for support to fund the establishment of a new research team to lead research aimed at exploring the physics of galaxy formation in the distant Universe. With three postdocs each year for a total of 5 years, we will pave new avenues towards understanding the relation between black holes and galaxies at the time of their major mass growth and assembly. In a full multiwavelength approach, by obtaining and using data from all major observational facilities (both in space and on the ground) we will aim to clarify the physical trigger of downsizing, catch AGN feedback in action and assess its role in galaxy transformations, along with the effects of the environment, gas accretion, star formation and merging in driving galaxy formation."