With the years passing, Homeworld was ruled by White and Yellow Diamond. We Creators saw no need to follow Gemkind's growth any longer. They had become an increasingly wise and kind species. Population size swelled, and Homeworld created many outposts on worlds. They chose worlds without intelligent life to settle on as opposed to some of our earlier interactions, though White and Yellow often argued the merits of settling and raising up other societies as we Creators had. As they clashed between one another they decided to leave the choice to Gemkind as a whole, and held a vote. Though close, it was ultimately decided to limit interaction with other species' for the foreseeable future.
Yellow Diamond set herself apart from her sister by focusing less on her kinds ability to shapeshift, and more in the limits of what Gems could themselves do. She became obsessed with synchronization of Gems. She felt that there must be something more Gems could do as she had personally witnessed some Gems enter some unknown state, similar to shape shifting...yet different. Two Gems would glow but no new effect would occur. The White Effect as it was known originally, was studied heavily by Yellow. The stumbling block in her research finally gave way when two Gems who were gemforming part of an offworld mountain. They triggered a landslide that would've cracked one of their gems. For reasons unknown when one Gem tackled the other to push the other out of the way they briefly coalesced into a singular being known as Zoisite. Though the form only lasted several minutes before coming undone it was what Yellow Diamond awaited all this time. Fusion was discovered.
But while Yellow Diamond reveled in her research panning out what she could not predict was a new member of her family having formed.
Homeworld welcomed its Blue Diamond.