  Polarized dust emission outside of disks reveal the magnetic field morphology
of molecular clouds. Within disks, however, polarized dust emission can arise
from very different mechanisms (e.g., self-scattering), and each of them are
useful for constraining physical properties in the disk. For example, these
mechanisms allow us to constrain the disk grain size distributions and
grain/disk geometries, independent from current methods of measuring these
parameters. To accurately model these features and disentangle the various
polarization mechanisms, multiwavelength observations at very high resolution
and sensitivity are required. With significant upgrades to current
interferometric facilities, we can understand how grains evolve in disks during
the planet formation process.
