Astronomers now know that supermassive black holes reside in nearly every galaxy. Though these black holes are an observational certainty, nearly every aspect of their evolution — from their birth, to their fuel source, to their basic dynamics — is a matter of lively debate. In principle, gas-rich major galaxy mergers are key to generate the central stockpile of fuel needed for a low mass central black hole ‘seed’ to grow quickly and efficiently into a supermassive one. When the black holes in each galaxy meet, they form a supermassive binary black hole, the loudest gravitational wave source in the Universe, with the energy to transform its galactic host. This talk will touch on some current and ongoing work on refining our theories of how supermassive black hole binaries grow, evolve within, and alter their galaxy host.