  Stellar feedback -- stars regulating further star formation through the
injection of energy and momentum into the interstellar medium -- operates
through a complex set of processes that originate in star clusters but shape
entire galaxies. A mature theory of stellar feedback is essential to a complete
theory of star and galaxy formation, but the energy and momentum injected by
hot gas into its surroundings remains unclear. With a next-generation X-ray
observatory, breakthrough progress can be made through precision measurements
of the temperature, density, velocity, and abundances of hot gas on scales of
star clusters to galactic superwinds.
