  Interstellar superbubbles generated by multiple supernova explosions are
common in star-forming galaxies. They are the most obvious manifestation of
mechanical feedback, and are largely responsible for transferring both thermal
and kinetic energy to the interstellar medium from the massive star population.
However, the details of this energy transfer remain surprisingly murky when
individual objects are studied. I will summarize what we currently know about
candidate dominant processes on these scales.
