Pluto is the farthest planet from the Sun (usually) and by far the smallest. Pluto is smaller than seven of the solar system's moons (the Moon, Io, Europa, Ganymede, Callisto, Titan and Triton).

In Roman and Greek mythology, Pluto (Greek: Hades) is the god of the underworld. After the fall of the Titans , Pluto and his brothers Zeus and Poseidon divided the universe, and Pluto was awarded everything underground. There, with Persephone as his queen, he ruled over Hades. Not only a god of the dead, he is identified as a god of the earth's fertility.