Much of our effort in understanding the long-term evolution and morphology of theMilkyWay 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.

This is a pre-published version which is collected from arXiv link. The published version is at http://www.aspbooks.org/a/volumes/article_details/?paper_id=22059