How Christina Aguilera Got 'Dirty'

July 4 -- How did Christina Aguilera, the sweet-faced teen whose first hit was for a Disney cartoon, turn into the semi-naked temptress bumping and grinding in her new orgy-like video, "Dirty"?

Her answer is simple: "I'm growing up, just like everybody does."

Aguilera rocketed to the top of the pop music world in 1999 with Reflection, the theme tune for Disney's animated film Mulan. (Disney is the parent company of ABCNEWS.com.) Her self-titled first album sold more than 12 million copies and won the Grammy for best new artist.

She was celebrated by fans across the world as the picture-perfect, all-American girl.

But just as she reached the top, she decided to destroy her squeaky-clean image. As well as "Dirty" — which opens with rapper Redman calling her "dirty, filthy, nasty" — her new album, Stripped, features songs like "Get Mine, Get Yours" and "Infatuation."

Critics have condemned Aguilera's sex-and-piercings image — she appears topless on the album cover, and nude except for a guitar on a recent cover of Rolling Stone magazine. They ask why such a good singer would feel the need to spice up her image.

But Aguilera, now 22, says she is no sellout. On the contrary, she says, she is for the first time refusing to fit the mold.

"If they don't like it, they don't have to look at it, you know? It's just as simple as that," she told ABCNEWS' 20/20.

Violence at Home

Aguilera grew up in the Rust Belt, just outside Pittsburgh. Her family life was far from perfect. According to her mother, her father had a violent temper — and her mother often bore the brunt of it.

When her parents were fighting, little Christina would run upstairs, shut the door, and escape — to where the hills were alive with The Sound of Music.

"I used to take that soundtrack to the movie up to my room, put it in my little boom box … line up my stuffed animals and open the window," she said. "I would pretend I was Maria."

When Aguilera was only 5, she and her mother fled the violence and moved in with her grandmother in Rochester, Pa.