Orbital decomposition of a typical TNG50 galaxy. We show the probability density distribution, p(r, λ_z) (left panel), and age distribution, p(r, t) (right panel) of the stellar orbits in the phase space of radius r versus circularity λ_z. The probability densities are normalized to unity within 3 R_e. The dashed black line marks our division into two stellar components: a dynamically cold disk component (λ_z ≥ 0.8) and a dynamically hot non-disk component (λ_z < 0.8). The dashed red line represents the effective radius, R_e, of this galaxy.