Deep surveys have revealed a population of very massive (M_* ? 10^10–10^11 M_?), extremely compact, quiescent galaxies at z ~ 2–3—so-called “red nuggets” with effective radii of only ~1–2 kpc, far smaller than similarly massive ellipticals today (Damjanov et al. 2009; van Dokkum et al. 2015). ΛCDM-based models can in principle grow these systems into present-day large ellipticals via minor mergers, adiabatic expansion, and structural puffing up, but they must invoke substantial, carefully tuned size growth while also explaining the apparent survival of some compact relics at low redshift, leaving open whether the full abundance, compactness, and evolutionary pathways of red nuggets arise naturally in the standard framework (Hopkins et al. 2009; de la Rosa et al. 2016).