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Britney Spears: Then

Back when Brit Brit first hit the scene in 1999, she had quite a thing for snug-fitting crop tops.

Britney Spears: Now

Touring the world to promote her album Femme Fatale, Britney's all, crop tops. Well, they are gonna be big for spring.

Britney Spears: Shop It

A modern-day take on the pop princess' fave abbreviated shirt.

Christina Aguilera: Then

In her "Dirrty"-er days, Xtina frequently picked lower-than-low denim, teensy tops, a beauty pageant's worth of bronzer and...blonde dreadlocks?

Christina Aguilera: Now

The golden-voiced songstress still favors a bold beauty look, but often chooses leather separates, black leggings and Louboutin pumps while playing judge on The Voice. And as for the occasional bit of backlash over her body-conscious picks and newfound curves, well, Christina would probably consider that something that makes her "a fighter."

Christina Aguilera: Shop It It

The roughed-up black leather finish and bevy of zippers makes this little topper totally Aguilera-esque.

Jessica Simpson: Then

Our December cover girl first hit it big in 1999, when she released her debut album Sweet Kisses. Her powerhouse pipes and girlish image were so sweet, in fact, that they helped her launch her own edible beauty collection, Dessert. She often hit the scene with her own personal man candy, boyfriend-turned-husband-turned-ex-husband Nick Lachey.

Jessica Simpson: Now

Business-savvy Jess is just as much a part of pop culture today. She recently collaborated with little sis Ashlee on a clothing line, helms her own billion-dollar business and is expecting her first child with fiancé Eric Johnson. Her life really is a public affair after all!

Jessica Simpson: Shop It

If there's two things Simpson's adored since her industry debut, they're designer Michael Kors and soft knitwear.

Mandy Moore: Then

Shortly after releasing her debut single "Candy," Mandy dyed her blonde locks brown, chopped them into an edgier pixie cut and began moonlighting as an actress in films like A Walk to Remember. She famously favored comfier duds than many of her pop contemporaries—especially Juicy Couture tracksuits and UGG boots.

Mandy Moore: Now

She's kept the brunette 'do, but stepped up her style game. Today, Mandy chooses fitted frocks in ladylike silhouettes from Marchesa and Monique Lhuillier.

Mandy Moore: Shop It

Mandy's favorite Juicy sweats, updated. All the comfort with none of the soccer-mom connotations.

Jennifer Lopez: Then

Back when it was somewhat believable that Jenny hailed from "the block," she stunned onlookers in dramatic red-carpet this iconic tropical-print Versace at the 2000 Grammy Awards.

Jennifer Lopez: Now

The artist formerly known as J.Lo still has a taste for the finer things in life. Now a judge on American Idol, Jennifer wows in jaw-dropping this Gucci dress she picked for the Met Gala back in May.

Jennifer Lopez: Shop It

Sheer? Check. Leopard-spotted? Check. Vibrantly colored? You bet. This one's got "J.Lo" written all over it.

Beyoncé Knowles: Then

As one of the founding members of girl group Destiny's Child, Beyoncé often took to the red carpet wearing shiny, figure-hugging getups designed by her mom Tina.

Beyoncé Knowles: Now

Years after striking out on her own with a solo career—and coupling up with rapper/mogul Jay-Z—Sasha Fierce still always manages to look, well, totally fierce. And her enthusiastic baby-bump reveal during her 2011 VMAs performance will go down in celluloid history.

Beyoncé Knowles: Shop It

Wonderfully similar to the sequined Dolce & Gabbana blazer B sported at the VMAs. And it was designed by another Hollywood heavy-hitter, so you know it's good.