Building a comprehensive picture for the evolution of galaxies from early times through present epoch requires understanding a huge dynamic range of physical processes. With observations ranging from detections of galaxies less than a billion years after the Big Bang to stellar and molecular cloud mass spectra in the Milky Way, the challenge has been to develop a concordance theory for galaxy formation than simultaneously explains this diverse range of observed galaxy properties across cosmic epoch. At the heart of many of the central questions in the astrophysics of galaxy evolution lies the physics of the interstellar medium, and galactic-scale star formation. In this talk, I will describe how understanding the complex interplay between small scale star formation physics and global galaxy evolution processes can lead to considerable insight in long-standing problems in both fields. I'll focus on two long-standing problems in the field: The origin of dusty galaxies at high- redshift, and the origin of variations in the CO-H2 conversion factor in molecular clouds.