Example of a massive clump hosting sub-structures, as a zoom-in on Fig. 1 (right panel, f_gas = 40%). The contours indicate the surface densities of molecular gas at 10, 100 and 1000 M_⊙ pc⁻². The red circles shows our clump identification. As visible in this example, some of the largest clumps host clear sub-structures, which are inexistent in smaller clouds (either physically or because of limited numerical resolution).