Scott Lang originally became a hero to help Cassie, who was suffering from a heart defect. As Cassie became older she wanted to become a hero just like her father. With Ant-Man for a dad, Cassie was able to encounter the world's greatest heroes on a frequent basis. Scott's time as an engineer for the Fantastic Four brought Cassie to the team's then headquarters of Four Freedom's Plaza. In the spectacular environment Cassie once called home she forged a strong friendship with the former ward of Dr. Doom, Kristoff Vernard. For the time they shared a home with the Fantastic Four, Cassie helped Kristoff adjust to life outside of Doom's castle, and she developed something of a crush on the boy.
After the Fantastic Four went missing and Scott found himself without a job, he found employment at Oracle, Inc. with the Heroes for Hire. It was while working with the Heroes for Hire that Cassie had further adventures, accidentally activating the Super-Adaptoid, and receiving horrifying visions of things to come. The H4H easily defeated the Adaptoid, and Cassie's participation in these dark events helped her father and his allies defeat the Master in a battle for the fate of the Earth itself. All of these exciting adventures gave Cassie a taste for the action-filled life of a super hero, but it caused her mother to take sole custody from Scott.
When Cassie's mother Peggy had remarried, she continued to harbor a growing resentment towards superhuman heroes. Peggy was able to obtain a court ruling limiting Scott's time with Cassie to supervised visits, causing him to join the Avengers after declining several invitations to join the famous heroes. Although she missed her father a great deal, Cassie was excited to spend time with the Avengers. She loved her father, and though she preferred living with him to her mother and new father-in-law, Blake Burdick, she was proud of Scott's successes as a hero and Avenger.
Cassie went through a traumatic experience during this time, being kidnapped and held hostage with the looming threat of violence from a deranged individual hanging over her head. Scott arrived in time to save Cassie, and nearly took the life of the crazed man who had taken Cassie from her school. Her father's teammate Jack of Hearts had followed closely behind his fellow Avenger, unwilling to let Scott make a fatal mistake before Cassie's very eyes. Jack did the avenging for Scott, and did so at the cost of his own life.
Having felt responsible for Jack of Heart's death, Scott ran out to greet his fallen comrade when he inexplicably landed on the Avengers Mansion grounds. Scott was incinerated when Jack suddenly exploded, leaving some skeletal remains of Ant-Man in the newly formed crater. The Avengers lost a great deal during the coming hours, leading to the apparent end of the team itself. Cassie Lang was left without the love and support of her father. He was her parent, her inspiration, her hero and more. The man who had meant so much to her had died. Cassie was very saddened by her father's death, but as one hero would leave this world, another would take his place.
Soon after the Avengers disbanded a group dubbed the Young Avengers first appeared. Not long after their first public adventure, Cassie Lang sought out and found the four teen boys called Iron Lad, Patriot, Hulkling and Asgardian (later changed to Wiccan). Along with another young woman who had befriended the team earlier in the same evening, Cassie confronted the Young Avengers in front of the remains of Avengers Mansion, discovering to her surprise, that she was able to grow to enormous heights with mere thought. Unbeknownst to her family and friends, Cassie had been secretly taking Pym Particles for some time at the time of her father's unexpected death. Initially, Cassie assumed her attempts at gaining superhuman abilities were fruitless, but that assumption was proven false as she grew to massive proportions in front of the Young Avengers and promptly fainted afterwards.
With the intention of becoming "the New Ant-Man," Cassie took her father's uniform. Wearing his costume she earned her place with the Young Avengers. During the eventful and fateful night where the Young Avengers were truly forged Cassie found a great friend in Kate Bishop, a fellow recruit to the YA team. During the turmoil Cassie even found romance in the form of a kiss shared with the team's founder, Iron Lad. Sadly, Cassie had to let her new love interest go for the good of the space-time continuum, and it appeared that the Young Avengers would be shut down for good by Captain America and Iron Man. But Cassie and Kate weren't going to allow that. Gathering the boys together some weeks after their momentous evening Cassie and Kate revealed their plan to unveil the Young Avengers to the world. Cassie had settled on the code name Stature, as she had demonstrated both growing and shrinking abilities, not unlike the first Ant-Man, Hank Pym.
It was an exciting time for Cassie, with her time as a Young Avenger filled with the adventure and fun she had missed since moving away from, and then losing her father. But Cassie's role as Stature was also bitter sweet. She felt as though she was betraying her mother Peggy in a sense, by becoming the very thing that Peg hated the most.
During the Civil War, Cassie originally sided with the other Young Avengers in rebelling against the Registration Act, but after Goliath was killed, she decided to register. She joined the Initiative and helped them battle the Skrulls during the Secret Invasion, but they were defeated. Nick Fury and his new team intervened and saved them.
When Wiccan summoned the Young Avengers on a mysterious threat, Cassie and Vision arrived, the other Young Avengers were turned to stone. The Scarlet Witch then appeared to whisk them away to form an new group of the Might Avengers.
When Cassie grows bigger, her Achilles tendons and nerve clusters grow in proportion, creating large, easy-to-hit targets.
Stature's costume is made of unstable molecules, allowing it to grow and shrink along with her. It appears to be based largely on her father's most recent uniform. Rather than the insect-controlling helmet of her father and his predecessor Cassie wears a domino mask.