Abstract. Spatially-and spectrally-resolved studies have proven very powerful in exploring the processes driving baryonic mass assembly and star formation at redshifts z ∼ 1 − 3, the heyday of massive galaxy formation. This contribution presents selected key results from near-infrared integral field spectroscopic studies of z ∼ 1 − 3 galaxies, including from the SINS/zC-SINF and KMOS 3D surveys with SINFONI and KMOS at the ESO Very Large Telescope, highlights synergies with observations at other wavelengths, and discusses some of the implications for early galaxy evolution from mass assembly to feedback processes.