The sole survivor of Argo City, Kara Zor-El, was sent to Earth by her scientist father to live with her cousin Kal-El, who had become known as Superman. Kara adjusted to her new life on Earth and became known as Supergirl. It was later discovered that Supergirl's parents had survived in the Survival Zone, a parallel dimension similar to the Phantom Zone, from which she released them. When the bottle city of Kandor was finally enlarged on a new planet that was similar to Krypton, Supergirl's parents joined its inhabitants to live there.