  `Superthins' are a subset of edge-on spiral galaxies exhibiting disks with
large axial ratios (a/b>10), extraordinarily small stellar scale heights, and
no bulge component. These are thus examples of dynamically cold, pure disk
galaxies. We have recently obtained multiwavelength (HI, optical, NIR)
observations for a large sample of superthin spirals. Our data lead to a
picture of superthins as `underevolved' disk galaxies in both a dynamical and a
star formation sense. Studies of these relatively simple disk systems can
therefore provide unique constraints on galaxy disk formation and evolution
without looking beyond the local universe. We present the results of a detailed
analysis of the nearby superthin UGC 7321 as an illustration of these ideas.

Astrophysics