Using two different kinds of state-of-the art numerical simulations, we discuss 1) formation of a spiral galaxy and its stellar/gaseous cores, and 2) multi-phase gas models in the circum nuclear region and their ‘pseudo-observations’ using 3-D non-LTE radiation transfer calculations for molecular lines. We found that a galactic core in a spiral galaxy seen in our N-body/SPH simulations coevolves with the galaxy itself, as a result the average mass ratio is about 0.01. The spin-axis of the core is frequently changed associating with major-mergers, where the mass accretion rate for the central 0.5 kpc is also temporally enhanced. We expect that the ‘obscuring molecular tori’ around AGNs is very inhomogeneous and turbulent on a pc-scale, and this could be resolved in the nearby active galaxies using the ALMA. We also found that the CO-to-H2 conversion factor (X-factor) calculated from 12CO (J = 1-0) is NOT uniformly distributed in the central 100 pc region, but $X_{\rm CO (J=3-2)}$ is more uniform, and ∼0.3×1020 cm−2 (K km s−1)−1 is suggested.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html