How do we Build Future X-ray Observatories to Study Galaxies?

Galaxies are key objects for the study of cosmology, the life cycle of matter, and stellar evolution. X-ray observations have given us a new key window into these building blocks of the Universe, that allows us to investigate their hot gaseous component. While significant advances in our knowledge are expected from Chandra and XMM, there is a number of fundamental questions that require a next generation of X-ray telescopes. These telescopes need to be 10-30 sqmeter class telescopes, with Chandra-like resolution, and with a suite of instruments allowing spectral imaging at moderate to high resolution.