  Asteroseismology is the only observational tool in astronomy that can probe
the interiors of stars, and is a benchmark method for deriving fundamental
properties of stars and exoplanets. Over the coming decade, space-based and
ground-based observations will provide a several order of magnitude increase of
solar-like oscillators, as well as a dramatic increase in the number and
quality of classical pulsator observations, providing unprecedented
possibilities to study stellar physics and galactic stellar populations. In
this white paper, we describe key science questions and necessary facilities to
continue the asteroseismology revolution into the 2020's.
