Out past Neptune are vast reservoirs of icy bodies that can become comets if they get poked into the inner solar system. The Kuiper Belt is a donut-shaped region beyond the planets that is aligned with the plane of the solar system. The Scattered Disk is an eccentric region, and the source of short-period comets. The Oort Cloud, which surrounds the solar system out to great distances, is the source of long-period comets. [11:40]