Discover the origin of dwarf planets in the Kuiper belt and how studying them will provide insight into the process of planetary formation. Host Neil deGrasse Tyson describes how the Kuiper belt is made of innumerable icy objects that are leftovers from the formation of the planets. Planetary scientist Alan Stern discusses different classes of planets, such as terrestrial and giant, and suggests that Pluto-like dwarf planets may be the dominant class of planet-like objects in the solar system. Stern also describes how the growth of dwarf planets was halted and how the study of them will provide insight into the process of planetary formation.