Is Multiphase Gas Cloudy or Misty?
  Cold $T \sim 10^{4}$K gas morphology could span a spectrum ranging from large
discrete clouds to a fine `mist' in a hot medium. This has myriad implications,
including dynamics and survival, radiative transfer, and resolution
requirements for cosmological simulations. Here, we use 3D hydrodynamic
simulations to study the pressure-driven fragmentation of cooling gas. This is
a complex, multi-stage process, with an initial Rayleigh-Taylor unstable
contraction phase which seeds perturbations, followed by a rapid, violent
expansion leading to the dispersion of small cold gas `droplets' in the
vicinity of the gas cloud. Finally, due to turbulent motions, and cooling,
these droplets may coagulate. Our results show that a gas cloud `shatters' if
it is sufficiently perturbed out of pressure balance ($\delta P/P\sim 1$), and
has a large final overdensity $\chi_{\mathrm{f}}\gtrsim 300$, with only a weak
dependence on the cloud size. Otherwise, the droplets reassemble back into
larger pieces. We discuss our results in the context of thermal instability,
and clouds embedded in a shock heated environment.
