Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union (IAU). This reclassification was due to the establishment of three criteria that a celestial body must meet to be considered a planet: it must orbit the Sun, be spherical due to its own gravity, and have cleared its orbital neighborhood of other debris. While Pluto meets the first two criteria, it does not meet the third because it shares its orbital zone with objects in the Kuiper Belt, an area of the solar system filled with icy bodies and remnants from the solar system's formation. Therefore, Pluto was reclassified as a dwarf planet, recognizing its unique characteristics that differentiate it from the larger planets in our solar system.