Based on the most widely accepted model for structure formation in the Universe, the massive galaxies we see today are the result of the merging of smaller structures. Looking far enough, and therefore far back in time, one should then be able to see galaxies getting smaller and smaller. To explore this issue we focus on quasars host galaxies and trace their properties up to redshift z = 2.5 (about 8 billion years in the past). Observations indicate that up to z ~ 2.5 quasar hosts are massive galaxies that are fully formed even at these early epochs. This is in partial disagreement with the hierarchical merging scenario, for the formation of massive spheroids.