Over the last 13 billion years, galaxies such as our own have assembled several hundred billion stars and a central black hole weighing at least a few hundred million solar masses. Understanding how, when and why galaxies assemble their stars and central black holes is a fundamental goal of modern astrophysics. In this talk I will present results from two ongoing projects. First, I will demonstrate that an actively accreting central black hole can bring star formation in the host galaxy to a resounding halt, which provides an observational resolution to a problem that has plagued galaxy evolution models for over a decade. Second, I will present preliminary results from a large-scale far-infrared spectroscopic survey of star-forming galaxies, highlighting the use of molecular absorption and emission features in diagnosing the physical conditions within the galaxies interstellar medium.