Scientific motivation: Observations reveal the presence of a supermassive black hole in the center of virtually every massive galaxy. Gas falling onto these monster black holes light up in powerful phenomena known as "active galactic nuclei" or "quasars" ("quasi-stellar objects"). Gravitational attraction leads to galaxies colliding and merging with each other, which may trigger quasar activity and lead to the formation of pairs or binaries of supermassive black holes. Understanding and observing such binaries, particularly as they themselves merge, would provide unprecedented troves of information toward testing the general theory of relativity (Einsteinâ€™s theory of gravity), measuring the expansion history of the Universe and understanding the physics of quasars. Project goals and outcomes: The goal of the project was to perform computer simulations of gas falling onto a supermassive black hole binary as the latter spiral toward each other and merge. Recent theoretical studies have suggested that such an event is promising both in its observability and its potential scientific yield. We performed successful simulations to model the early stages of the binary in-spiral, but additional work is necessary to continue the calculations to the binary merger and its aftermath. The preliminary results from our work has since been presented at several international conferences. Although the NSF-funded fellowship lasted less than three months, it has led to a long-term and long-distance collaboration between the visiting and hosting scientists. Joint work on this and related projects continue. It is our hope that images and videos of completed simulations can be disseminated to the public (e.g., via public websites such as YouTube) to promote the most current work in this exciting and emerging subject.