  Supernovae are expected to occur near the molecular material in which the
massive progenitor star was born, except in cases where the photoionizing
radiation and winds from the progenitor star and its neighbors have cleared out
a region. The clumpy structure in molecular clouds is crucial for the remnant
evolution; the supernova shock front can become radiative in the interclump
medium and the radiative shell then collides with molecular clumps. The
interaction is relevant to a number of phenomena: the hydrodynamics of a
magnetically supported dense shell interacting with molecular clumps; the
molecular emission from shock waves, including the production of the OH 1720
MHz maser line; the relativistic particle emission, including radio synchrotron
and gamma-ray emission, from the dense radiative shell; and the possible
gravitational instability of a compressed clump.
