Kara Zor-El was the last survivor of Argo City of the planet Krypton, which had survived the explosion of the planet and had drifted through space. When the inhabitants of the colony are slain by green kryptonite which was released by metorites striking the lead barrier, Kara is sent to Earth by her father Zor-El to be raised by her cousin Kal-El, known as Superman. Fearing that she might not be recognized by Superman, Kara's parents provide a costume based on the Man of Steel's own.