  Interstellar dust is still the dominant uncertainty in Astronomy, limiting
precision in e.g., cosmological distance estimates and models of how light is
re-processed within a galaxy. When a foreground galaxy serendipitously overlaps
a more distant one, the latter backlights the dusty structures in the nearer
foreground galaxy. Such an overlapping or occulting galaxy pair can be used to
measure the distribution of dust in the closest galaxy with great accuracy. The
STARSMOG program uses HST observation of occulting galaxy pairs to accurately
map the distribution of dust in foreground galaxies in fine ($<$100 pc) detail.
Furthermore, Integral Field Unit observations of such pairs will map the
effective extinction curve in these occulting galaxies, disentangling the role
of fine-scale geometry and grain composition on the path of light through a
galaxy.
  The overlapping galaxy technique promises to deliver a clear understanding of
the dust in galaxies: the dust geometry, a probability function of the amount
of dimming as a function of galaxy type, its dependence on wavelength, and
evolution of all these properties with cosmic time using distant, high-redshift
pairs.
