Observations show that 6 < z < 7.5 quasars are powered by super massive black holes (SMBHs, MBH ≥1.e9 Msun), whose formation is one of the biggest mysteries for current theoretical and observational cosmology. The most recent JWST observations have revealed the presence of intermediate massive black holes (IMBHs, MBH ~1.e6-1.e7 Msun) in galaxies at even higher redshifts (z~10-11) than currently known quasars. Models suggest that SMBHs grow through gas accretion onto massive seeds, the so-called “direct collapse black holes” (DCBHs, MBH ≥ 1.e5 Msun). The growth of such massive black holes is regulated by feedback processes that may quench their host galaxy's star formation and reduce the gas accretion efficiency. The motivation for this focus week is to bring together different communities that investigate the physical properties of early massive black holes both from the observational and theoretical point of view to trigger new ideas and solutions about the problematic existence of massive black holes at high redshift.