  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.
