Long ago, more than 5500 years, there was a Great War on Earth. This war was between alien gem rebels and their own kind from a planet that called Homeworld.
The leader of the rebellion, Rose Quartz, believed that all life was precious and worth protecting. Starting with only herself and Pearl, Rose Quartz began a group of rebels called the Crystal Gems and bravely flight against their Homeworld. After many years of fighting, losing countless gems and humans, the rebels triumphed and and won the war. However, in the end Rose was only able to save a handful of her closest friends.
Time went by, and life was good for the Crystal Gems. Now the group only consisted of Rose Quartz, leader of the rebellion, Pearl, Rose's second hand assistant, Amethyst, a defective quartz Rose found in the Kindergarten after the war, and Garnet, a permafusion of love consisting of the gems Ruby and Sapphire.
Despite the fact that the Crystal Gems were the sworn protectors of the humans, they kept their distance from them and even kept a fence around their base. Eventually, a young man, named Greg, followed Rose over the fence. They were always together after that night.
After a few years, Rose was pregnant with a child. However, at a great price, Rose would have to give up her physical form forever to give birth to the child. She did it, though, and Rose Quartz gave the world Steven Universe, and that was only the beginning.