Mass-weighted Sérsic index, obtained from GALFIT, as a function of distance from the MS, Δ_MS, for the low- and high-redshift samples (left and right panels, respectively). The three stellar mass bins are represented with different colours. At all stellar masses, galaxies below the MS are more compact than MS counterparts, while galaxies above the MS have a similar or lower Sérsic index than MS sources. An increase of the Sérsic index is visible on the MS relation, with increasing stellar mass.