  From the IllustrisTNG-50 simulation, a sample of 836 central disk galaxies
with tiny stellar halos is chosen to study the inherent evolution of galaxies
driven by nature. These galaxies are classified as compact, normal, or extended
by referencing their locations on the mass-size ($M_\star-R_{\rm 1/2}$)
diagram. This research demonstrates the distinctive evolutionary pathways of
galaxies with different sizes in IllustrisTNG simulations, primarily driven by
nature. It is confirmed that disk galaxies inherit the angular momentum of
their parent dark matter halos. More compact galaxies form earlier within halos
possessing lower specific angular momentum through heightened star formation
during the early phase at redshifts above 2. During the later phase, the size
of extended galaxies experiences more pronounced growth by accreting gas with
high angular momentum. Additionally, we reveal that many key characteristics of
galaxies are linked to their mass and size: (1) compact galaxies tend to
exhibit higher metal content, proportional to the potential well
$\frac{M_\star}{R_{\rm 1/2}}$, (2) compact galaxies host more massive bulges
and black holes, and higher central concentration. Furthermore, our analysis
indicates that galaxies of all types continue to actively engage in star
formation, with no evident signs of quenching attributed to their varying sizes
and angular momenta.
