Scarlett's 'Island'

(CBS)  At 20, Scarlett Johansson is one of a few young actresses who can say that she's been a movie star for more than half her life.

With a variety of notable films under her belt, Johansson has quickly become one of Hollywood's "It" girls. Her latest is the big-budget futuristic thriller, "The Island." In it, she stars with Ewan McGregor as residents of a facility. They apparently have survived a worldwide disaster, and are hoping to be chosen for the last uncontaminated paradise on Earth.

Explaining the film, Johansson says, "We're all just kind of happy-go-lucky, waiting for our chance to win the random raffle so that we can go to the island. It's the only place on Earth that has clean water and air."

Then McGregor's character starts asking questions ("as all creatures do," says Johansson): Why are we here? What are we doing?

As Johannson explains it to Early Show co-anchor Rene Syler, "We're all evolving and his brain is starting to question: 'Where do they keep finding these new people anyway? What are these jobs we're doing?' And my character just says, 'Why do you have to ask all these questions all the time? Not all wonderful things have a bad side to them.'"

The truth is that "The Island" is inhabited by human clones whose only purpose is to provide spare parts for their original human donors. Faced with the fact that their existence is essentially a lie, the characters played by Johannsson and McGregor mount a harrowing escape from the only life they've ever known.

Their roles seem physically taxing, as both stars keep being chased, making it necessary for them to duck and jump, and Johansson agrees.

"I'd never run so much in my entire life," she says, "You read the script and you go to yourself: 'Oh, wow, what she's doing is sliding down a drain pipe. Well, that sounds interesting.' Then, of course, the day of the scene, you;ve got to slide down this drain pipe. You are thinking: 'What!?'"

"The Island" is Johansson's first summer blockbuster. She made her film debut at age 9, but unlike many of her acting contemporaries, Johansson has grown up on the big screen choosing roles in diverse smaller films, with much critical acclaim. She has starred alongside Hollywood heavyweights like Robert Redford in "The Horse Whisperer," Bill Murray in "Lost In Translation," John Travolta in "A Love Song For Bobby Long," and Dennis Quaid in "In Good Company."

"As any creative person, you don't want to be stuck in a box," says Johansson, "Somebody saying, 'Well, you fit in the young, passive ingénue category.' And you don't want to get stuck doing that. You don't want to get stuck doing teen comedies. You don't want to be the scream queen, you know?"

There seems to be also an incredible pressure among actresses in Hollywood to stay fit. It's really not realistic, but Johansson tells Syler the only pressure she feels is that which she puts on herself.

"If I look in the mirror and I say, 'Hmmm sagging a little bit,' I hit the gym," Johansson says, but admits there is a lot of pressure.

She says, "It's crazy, asking people or, my goodness, especially when you see them in person if they're as bad in a photograph. It shouldn't be like, 'Oh my God. Did you see how skinny she was? That's not sexy.' You got to have a little something cuddle up too; sometimes it's a little more than you'd like it to be. That's when you hit the gym.

Next for Johansson is Brian De Palma's "The Black Dahlia."