Detailed Semi-Analytic Models (SAMs) of galaxy formation often reach opposite conclusions on how early-type, bulge-dominated galaxies have formed and evolved. Hierarchical models predict a fraction of their stars formed in a fast, high-redshift burst of star formation, and the rest assembled later on via a sequence of (mostly gas-poor and minor) mergers. Monolithic models propose instead that most of the stars were formed in the initial burst. On other grounds, deep observations have now showed that massive spheroids at high redshifts, are much more compact than their local counterparts. Moreover, in recent years, dynamical observations have revealed that Supermassive black holes (BHs) are ubiquitous at the centres of all local early-type galaxies. These observations show that tight correlations exist between the mass of the BH and the bulge and velocity dispersion of the host. Hierarchical models predict that the late assembly of galaxies (and their BHs), can efficiently ``puff-up’’ their sizes, while monolithic models claim that the size evolution is mostly driven by a quasi-adiabatic, slow expansion consequent to strong mass loss caused by quasar and stellar feedback.In this project we propose to shed light on massive galaxy evolution by carrying out an extensive research based on exploiting state-of-the art purely hierarchical and mixed models for galaxy evolution. We will compare the predictions on mass, size, profile, velocity dispersion, and number density evolution of massive galaxies and their connection with central BHs, with a variety of new data sets derived from large and deep surveys of massive galaxies led by our group, such as COSMOS, NGVS and the local SDSS. We will also make use of detailed numerical simulations performed by our group, that will allow us to set definite answers on some theoretical predictions such as the expansion of galaxies.