As a young girl, Cassie's father, Scott Lang, adopted the guise of Ant-Man to help save her life. After her mother divorced her father, she grew up idolizing her father's adventures with the Avengers. When her mother and stepfather grew uneasy about Scott's life as an Avenger, she filed, and won, full custody of Cassie, and unsuccessfully tried to shield her from superheroes. Cassie continued to visit her father until the his death.
Afterwards, Cassie retreated to herself, shunning her mother and stepfather's attempts to reach out to her. Secretly the superhero life continued to call to her, and the disaffected Cassie toyed with the idea leaving her home and joining the Los Angeles-based rogue team of young heroes known as the Runaways. After seeing a story on TV about the Young Avengers, she sought them out, becoming a full member.
Civil War|More recently, Cassie, along with her fellow Young Avengers joined Captain America's resistance to the Superhero Registration Act. She, and the other Young Avengers, also attempted a mission to recruit the Runaways to the Anti-registration cause, battling the U.S. Government and a rogue Kree warrior in the process. However the strain of the Super-hero Civil War has taken its toll on the young heroine and she has recently split with Captain America's resistance -- and her own teammates.