Mass-size relation for galaxies E (red star) and W (green star) in B14-65666, together with clumps of SMACS0723 at redshifts 6.4–8.5 (yellow squares, Claeyssens et al. 2023) and a subsample of massive and compact galaxies from the CEERS program (purple circles, Baggen et al. 2023). The blue line represents the mass-size relation for galaxies (blue dots) at redshifts 4–10 (Langeroodi & Hjorth 2023), while the solid black line indicates the mass-size relation for redshifts 6–9 derived for the NIRCam filter F150W (Allen et al. 2025). As B14-65666 is an interacting system, we also represent the mean values of the mass and size for local LIRGs and MS SFGs (Bellocchi et al. 2022) and (Leroy et al. 2021). Dotted gray lines represent constant stellar mass surface density for 10, 10², 10³, 10⁴, and 10⁵ M_⊙ pc⁻². The red line indicates the observed maximum value of stellar-mass surface density in clusters and nuclei of galaxies, 10^5.5 M_⊙ pc⁻².