Galaxy evolution in mass-selected samples

I summarize the recent results from the HDFS and K20 surveys that allow to trace the evolution of massive galaxies up to z similar or equal to 3. I show that the evolution of both the specific star-formation rate and of the stellar mass density suggest that, at z > 1, we observe the epoch where the evolution of massive objects becomes appreciable. At z similar or equal to 1.8, we indeed find that about 40% of the local density has been locked in massive galaxies. This is associated with a change in the physical properties of massive galaxies, with star-forming objects that contribute to a substantial fraction of the observed mass density. I quantitatively show that these results do not pose challenges to current Lambda - CDM models, but represent valuable constraints to understand the complex physical mechanisms involved in the assembly of massive galaxies.