Spitzer view on galaxy evolution in the last 12 Gyr

I will discuss our analysis of Spitzer data in combination with other multi-wavelength observations to improve our understanding of galaxy formation and evolution in the last 12 Gyr. Our research is focused on two different topics: (1) getting better SFR estimates for individual galaxies and sub-galactic structures; and (2) linking the SFR density evolution of the Universe with the assembly of the stellar mass of galaxies. In the first topic, we argue on the need of combining optical and infrared data to obtain the best estimations of the SFR of individual objects accounting for the two modes of star formation, linked to UV-bright unobscured and IR-bright dusty environments. In the second topic, we quantify the downsizing theory by studying the evolution of the stellar mass function of the global population of galaxies and of the star-forming sources during 90% of the age of the Universe (up to z=4).