A complete understanding of their formation and evolution requires detailed dynamical treatment of the disks and spheroids stars as they behave in isolation in response to internal instabilities and as they behave in a cosmic environment where they interact and merge with other galaxies.

A big current goal is to understand the dynamical evolution of galaxies over cosmic history as they interact in clusters and the field and are transformed from spirals into ellipticals in mergers. New observations of distant and young galaxies are pressing the need for detailed modelling of galaxy interactions in cosmological environments to test for consistency with the current cosmological paradigm. Dubinski has been a pioneer in using parallel, N-body simulations to study the galaxy interactions in clusters. He has been pushing the limits of current technology, simulating N-body systems of hundreds of disk galaxies falling into a cluster using tens of millions of particles. High resolution is needed to follow dynamical evolution faithfully over a Hubble time. From the analysis of over 200 hundred merger remnants, it appears that the fundamental plane relations for ellipticals result from simple dissipationless merging of spiral galaxies.