- "Long ago, in an era of expansion, our race spread throughout the stars seeking new worlds to settle upon. This scout ship was one of thousands launched into the void. We built outposts on other planets, using great machines to reshape environments to our needs. For 100,000 years, our civilization flourished, accomplishing wonders."
The Kryptonian expansion, referred to by Kryptonians as the "Great Age of Expansion," was a campaign led to explore the known universe and beyond. Due to the advancement in genetic engineering on Krypton, the program was ended and the outposts were abandoned.
As the expansion campaign kicked off, Kryptonian scientists created exploration vessels meant for deep-space travel, capable of sustaining a small crew for their journey into uncharted space sectors to find new worlds to colonize.
During numerous explorations Kryptonians encounterd other sentient species such as Thanagarians and New Gods. At some point before 1980 they discovered the existence of humans on the planet Earth.
When she was of age to join, Kara Zor-El enlisted into the Explorer Guild to train as a pilot for the newly developed scout ships. After graduating, Kara was granted her own ship and crew, having trained extensively to learn how to survive in possible environmental conditions in preparation for her mission.
The Kryptonian Expansion's purpose was to explore the known universe and beyond, discovering new worlds. When many Kryptonians arrived on new worlds, they built outposts, using great machines called World Engines to reshape the world's environment to what they want. This process lasted for over 100,000 years and civilizations increased, accomplishing many goals.
- "What happened?"
"Artificial population control was established. The outposts and space exploration was abandoned. We exhausted our natural resources. As a result, our planet's core became unstable. Eventually, our military leader, General Zod, attempted a coup. But by then it was too late."
- ―Kal-El and Jor-El[src]During the period, Kryptonian civilizations on outposts were having a lack of natural resources. This resulted in Kryptonian outposts dying out due to being abandoned by the main government of Krypton. Eventually, Krypton itself started to run out of resources, which led to a careless mining in Krypton's planetary, radioactive core, thereby destabilizing the core and causing the planet to explode. The Kryptonian Expansion ended, with only a critical amount of Kryptonians left throughout the universe.