  Tremendous progress has been made recently in modelling the morphology and
kinematics of centers of galaxies. Increasingly realistic models are built for
central bar, bulge, nucleus and black hole of galaxies, including our own. The
newly revived Schwarzschild method has played a central role in these
theoretical modellings. Here I will highlight some recent work at Leiden on
extending the Schwarzschild method in a few directions. After a brief
discussion of (i) an analytical approach to include stochastic orbits (Zhao
1996), and (ii) the ``pendulum effect'' of loop and boxlet orbits (Zhao,
Carollo, de Zeeuw 1999), I will concentrate on the very promising (iii)
spectral dynamics method, with which not only can one obtain semi-analytically
the actions of individual orbits as previously known, but also many other
physical quantities, such as the density in configuration space and the
line-of-sight velocity distribution of a superposition of orbits (Copin, Zhao &
de Zeeuw 1999). The latter method also represents a drastic reduction of
storage space for the orbit library and an increase in accuracy over the
grid-based Schwarzschild method.
