  Much of our effort in understanding the long-term evolution and morphology of
the Milky Way and other galaxies has focused on the equilibrium of its luminous
disk. However, the interplay between all components, seen and unseen, is a
major cause of observed features and drives evolution. I will review the key
underlying dynamics, and in a number of examples, show how this leads to
lopsidedness and offset nuclei, may trigger bars and cause warps. Indeed, the
Milky Way like most spiral galaxies show exhibit many of these features. In
addition, the mechanisms suggest that observed morphology depends on the
properties of the galaxy and only weakly on any particular disturbance. Because
of this convergence, understanding a galaxy's history will be subtle and
require the level of detail that study of the Milky Way can provide.
