21 & Under: Hottest Breakout Stars

Zac! Rihanna! Shia! Lauren! These kids aren't only the most popular, they're also the most likely to get bigger in '08. By Aaron Parsley

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THE CALIFORNIA GIRL

When this Laguna Beach alum packed up and moved to Hollywood with a reality camera crew in tow, Lauren Conrad's 15 minutes could've run out fast. But when the 21-year-old It girl with the enviable wardrobe and relatable social life turned The Hills into a screaming match with nemesis Heidi Montag ("You're a bad person!"), you couldn't help but pick a side and watch her every text message.