In the standard Lambda cold dark matter (Lambda-CDM) cosmology, galaxies grow by gradually accreting material and through mergers with other galaxies. This scenario successfully explains many large-scale cosmic structures, yet it struggles to account for the existence of numerous massive spiral galaxies in the local Universe that lack a prominent central bulge, pure disc systems, in the local Universe. Understanding how these galaxies form and survive is also essential for placing our own Galaxy, the Milky Way, into context, as it also hosts a low-mass bulge. In this study, we analyse 22

Measuring galaxy sizes is essential for understanding how they were formed and evolved across time. However, traditional methods based on l ight concentration or isophotal densities often lack a clear physical meaning. A recent study from Trujillo+20 explores a more physically motivated definition: the radius R 1, where the stellar surface density falls to 1 solar masses per parsec square —roughly the threshold for gas to form stars in galaxies like the Milky Way. In this work, Arjona-Gálvez+25 uses over 1,000 galaxies from several state-of-the-art cosmological simulations (AURIGA, HESTIA