The Jam Song I Steven Universe I Cartoon Network

The series is set in the fictional Beach City on the Delmarva Peninsula[5] on the American East Coast, where the Crystal Gems live in an ancient beachside temple, protecting humanity from monsters and other threats. Ageless alien warriors, they project feminine humanoid forms from magical gemstones that are the core of their being. The Crystal Gems are Garnet, Amethyst, Pearl and Steven, a young half-human, half-Gem boy who inherited his gemstone from his mother, the Crystal Gems' past leader Rose Quartz. As Steven tries to figure out his gradually expanding range of powers, he spends his days with his human father Greg, his friend Connie, the other people in Beach City, or the Gems. He explores the abilities passed down to him by his mother, which include fusion—the ability of Gems to merge their bodies and abilities to form new and more powerful personalities.

The first season slowly reveals that the Crystal Gems are remnants of a great interstellar civilization. Many places they visit are ruins once important to Gem culture, but now derelict for millennia. The Gems are cut off from their homeworld, and Steven learns that many of the monsters and artifacts they encounter are Gems who, corrupted by a Gem weapon of mass destruction, can no longer maintain rational humanoid forms. In parallel, flashbacks relayed by Greg develop the history of Rose Quartz and her relationships. By the end of the first season, Steven learns that the Homeworld Gems intended to sterilize the Earth to incubate new Gems within it. Now, 5,000 years after Rose led the other Crystal Gems in a violent and apparently successful rebellion against these genocidal plans, the Homeworld's machinations once again extend towards the Earth with the arrival of two hostile envoys, Peridot and Jasper. In the second season, Peridot is forced to ally with the Crystal Gems to prevent Earth's destruction by a Gem abomination growing in the planet's core. In the third season, Peridot and Lapis Lazuli, an errant Homeworld Gem, join the Crystal Gems. Jasper is at length defeated, and Steven learns that his mother killed one of Gem society's four matriarchs, Pink Diamond.