Understanding the connection between mass assembly and star-formation rate is a key question in galaxy formation. It is now well-established that a significant fraction of this mass assembly actually occurred in heavily dust-enshrouded environments as uncovered by sub-mm observations. I will present our latest results on the assembly history of massive dust-enshrouded galaxies obtained from the SCUBA Half Degree Extragalactic survey (SHADES), initially at 850 μ, and recently complemented by a very wide-field survey at 1.1 mm exploiting the AzTEC camera. I will compare these results with the evolution and assembly history of the whole population of "mass-selected" galaxies obtained by exploiting the very deep, large area, multi-wavelength dataset available in the UKIDSS Ultra Deep Survey. I will focus on the emergency of the red sequence at z ~ 2 and explore the connection between various populations of galaxies which have been discovered at high redshift (e.g. Lyman-break galaxies, Extremely Red Galaxies, sub-mm galaxies). I will also compare these results with the predictions of the latest models of galaxy formation and highlight the future role of deep near/mid infrared spectroscopy with new generation facilities as KMOS on VLT and JWST. Finally I will briefly present our latest results on the quest for primeval galaxies into the epoch of re-ionization at z > 7 obtained by exploiting the new camera WFC3 on Hubble.