  The workshop on Small Ionized and Neutral Structures in the Interstellar
Medium featured many contributions on the theory of the objects which are
responsible for ``Tiny Scale Atomic Structures'' (TSAS) and ``Extreme
Scattering Events'' (ESE). The main demand on theory is accounting for objects
that have the high densities and small sizes apparently required by the
observations, but also persist over a sufficiently long time to be observable.
One extensively-discussed mechanism is compressions by transonic turbulence in
the warm interstellar medium, followed by thermal instabilities leading to an
even more compressed state. In addressing the requirements for overpressured
but persistent objects, workshop participants also discussed fundamental topics
in the physics of the interstellar medium, such as the timescale for
evaporation of cool dense clouds, the relevance of thermodynamically-defined
phases of the ISM, the effect of magnetic fields, statistical effects, and the
length and time scales introduced by interstellar processes.
