X-ray Observations of Galaxies: The Importance of Deep High-Resolution Observations

X-ray observations of galaxies have grown from a curiosity into a full-fledged field of astronomy. These observations provide unique information on black holes, binary stars, and the hot phase of the ISM, which can be used to constrain the chemical evolution of the Universe, and the joint evolution of galaxies and massive black holes. These exciting results are due in large part to the high-resolution capability of {\it Chandra}. To follow on {\it Chandra} and push forward this science past the present capabilities, our community must build a high-resolution (sub-arcsecond) large-area (several square meters) X-ray telescope.