Overview of “Amaryllis”, a digital twin of early galaxies. Upper-left panel: Merger history of Amaryllis. Each curve shows the stellar mass (M_★) of the progenitors as a function of cosmic time (t), with the corresponding redshift (z) on the upper axis. The black line indicates the main galaxy, while each colored line represents a merging satellite. Solid lines mark the phases during which each system remains distinct, and dashed lines highlight the mergers. The observational measurements shown include massive z > 10 galaxies, spectroscopically confirmed by JWST (violet triangles; Ferrara et al. 2025, Table 1), z ∼ 6 − 9 galaxies from CEERS and COSMOS (green triangles; Harikane et al. 2024), and REBELS sources (red triangles; Dayal et al. 2022, Table 2). Upper-right panel: SFH of Amaryllis throughout cosmic time, with vertical lines corresponding to minor (dotted) and major (dashed) merger events. Bottom panels: Composite images at four evolutionary stages, built from the stellar surface density (Σ_★), gas surface density (Σ_gas), and the Habing field intensity (G).