Pluto spent seventy-six years as the solar system's ninth planet until the International Astronomical Union reclassified it as a dwarf planet in 2006, a decision that still divides astronomers. This film traces that controversy back to Clyde Tombaugh's 1930 discovery, then follows NASA's New Horizons probe on its nine-year, three-billion-mile journey to reach the Kuiper Belt object in 2015. Mission footage and animations reveal what the flyby actually found: towering water-ice mountains, frozen nitrogen plains in the heart-shaped Tombaugh Regio, a thin layered atmosphere, and evidence pointing to a subsurface ocean that could, in theory, host extremophile life. Planetary scientists explain how these findings upended assumptions that small, distant worlds must be geologically dead. The debate over Pluto's planetary status runs alongside the science, framed not as a settled argument but as a case study in how definitions shape what we think we know about the solar system's edge.