Size-mass relation at a redshift of 7, providing a more detailed view compared to Fig. 5. Clumps are color-coded by age, with blue indicating younger clumps and red representing older clumps. Clumps have been further grouped into age bins: clumps younger than 0.16 Gyr, between 0.16 Gyr and 0.31 Gyr and older than 0.31 Gyr, with each bin containing an equal number of objects. The isodensity contours for the three age distributions are also shown as dashed blue (young), yellow (intermediate-age) and red (old) lines. The grey vertical lines and bands represent the region of space where t_diss ≤ 13 Gyr, with t_diss the same as in Equation (12). Each line corresponds to a different assumption on R_G in Equation (12), specifically, from left to right, R_G = 18 kpc, 12 kpc, 6 kpc, 3 kpc, together with V_G = 220 km s⁻¹ to mimic the tidal field of MW like galaxy (see text for details).