Which two planets do scientists comets come from?

Scientists believe that comets primarily originate from two regions in the solar system: the Kuiper Belt and the Oort Cloud. The Kuiper Belt, located beyond the orbit of Neptune, contains icy bodies that can become comets when they are perturbed. The Oort Cloud, a distant and spherical shell surrounding the solar system, is thought to be the source of long-period comets that can travel from far beyond the planets.