"Gems" are an extra-terrestrial species of "magical" beings that play a central role in Steven Universe. They are sentient gemstones that can project a tangible, humanoid form. They are an intergalactic race which 5,750 years ago maintained several outposts on Earth, with plans to completely colonize the planet, but were driven off by Rose Quartz's rebellion, leaving the Crystal Gems, and the corrupted Gems, the only Gems on the planet, except for a small group of stranded Gems from the Gem Homeworld.