The Kuiper Belt consists of a large population of proto-comets.
The first Kuiper Belt Object was found in 1992 by David Jewitt and Jane Luu of the University of Hawaii. Astronomers have found over 400 KBOs, which are believed to be remnants from the formation of the Solar System.
The existence of the Kuiper Belt was postulated by J. A. Fernandez, M. Duncan, T. Quinn, and S. Tremaine in the 1980s, because short period comets found orbiting in the plane of the elliptic could not originate from the Oort Comet Cloud.
Currently the largest known object in the Kuiper Belt is known as “2001 KX76“. It was discovered by Astronomers from Lowell Observatory, the Massachusetts Institute of Technology, and the Large Binocular Telescope Observatory, and is roughly the size of Pluto's moon Charon.