1990s:

From Child Model to Actor

At 10, Leighton Meester decides she wants to be an actress. But she gets her start as a child model, signing with Wilhelmina Models and appearing in Ralph Lauren ads. At 13, after relocating from Florida to New York City, she makes her TV acting debut on an episode of Law & Order. "You ask people when they've just finished college what they want to do and they have no idea, and sometimes they never know," she tells Australia's Herald Sun. "But actors seem to know at an early age. I was lucky that I had such supportive parents."

2004: July 25

Entourage: Virgin Territory

After appearing as Jane's sister in the WB's failed series, Tarzan and Jane, Meester plays virginal pop singer Justine Chapin on the HBO hit Entourage. In the episode, Jessica Alba – who appears as herself – invites the boys to a party she's throwing for Meester's character, who flirts with movie star Vince Chase (played by Adrian Grenier, right).

2005: January 09

24: Poisoned Tea

Meester heads to Fox's 24 as Debbie Pendleton (left) in the acclaimed show's fourth season. She plays the American girlfriend of Behrooz Araz (played by Jonathan Ahdout) and gets poisoned by Araz's mother in her four episode-run. Meester also appears on Veronica Mars, with Kristen Bell, House M.D., and CSI: Miami.

2007: September 19

Gossip Girl: Being Blair Waldorf

Meester dons headbands and slathers on the lip-gloss to play the vengeful Queen Bee, Blair Waldorf, in Gossip Girl, The CW's adaptation of the juicy novels by Cecily von Ziegesar. The teen soap follows a group of rich New York City Upper East Siders. "It's an exceptional show and so true to life," Meester (pictured with onscreen boyfriend Chace Crawford) tells WWD. "People who live in that world are going to blush and be very bashful about how true to life it is." The series costars Blake Lively (Blair), Penn Badgley (Dan), Ed Westwick (Chuck) and Taylor Momsen (Jenny).

Leighton's Star Style Shines

As Gossip Girl becomes TV's favorite guilty pleasure, Meester becomes a style star off-camera with costar Blake Lively (right). "I wish I had the money for style like that," Meester tells WWD of her character's luxe wardrobe. "She's a little bit Audrey Hepburn old movie star and a little bit Charlotte from Sex and the City. Everything she wears is exactly appropriate to where she's going, and it's important for her to stand out but look dignified." Adds costume designer Eric Daman, who previously worked with Patricia Field on SATC, "These girls are very into fashion. They know what's going on and we're just trying to keep it contemporary."

2008: March

Leighton Makes Cover Debut

Meester appears on the cover of Teen, where she discusses her alter ego, Blair. "I feel like I'm becoming more like her and she's becoming more like me," she says. "She's young and vulnerable, but also smart and feisty. She's pretty funny and very strong-willed. Then there are other things I don't relate to and I feel like she'll grow out of, like her insecurities and self-doubt." As for the identity of Gossip Girl, she says, "I have my suspicions...If I had to guess, I was thinking it could be Chuck. He seems just evil enough to say those things."

2008: April 28

Gossip Girl Cast Covers New York!

The cast of Gossip Girl strips down for a tantalizing cover of New York magazine, which calls the teen soap, "the most awesomely awesome show ever." The magazine says of Meester, "Her villain-you-want-to-root-for is the most sophisticated performance on the show." That week, the entire cast also lands on PEOPLE's Most Beautiful List.