Compactness, 𝒞, as a function of the ratio between the stellar mass at z = 2, M_*(z = 2), and the mass of the main progenitor at z = 3 M_∗,pr1(z = 3) (left panel) and as a function of the ratios between the mass of the three most massive progenitors (first and second with M_∗,pr2 on the middle panel; first and third with M_∗,pr3, on the right panel) for EH (blue) and SH (red) galaxies. The shaded areas define regions of galaxies that would grow through major mergers of low-mass galaxies but would end up as NUC: there is no SH galaxy and only one EH galaxy in the three areas at the same time.