Guess the Celebrity #TBT!

This fashion-forward singer was apparently totally fierce as a kid. Captioning her photo with a simple "Throwback!" we're not surprised the bootylicious songstress brought in more than 300,000 comments from fans. She's a true triple threat with a body to die for and a voice to match, so who is she?

Was there ever a time when Queen Bey didn't look glam?! She's always pushing herself to be her best, and her body is no different. From grueling dance rehearsals, lots of cardio, and intense pre-tour gym sessions, no wonder the pop superstar looks so fab!

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She just might be one of the most charming females in Hollywood, and by the looks of her #TBT photo, her younger years were exactly the same! The Oscar winner writes, "#tbt don't worry I've been properly medicated since this photo." Do you know this actress?

Aside from her sparkling personality, we love how refreshingly honest Jennifer Lawrence is. The 23-year-old Hunger Games star recently told ELLE Magazine, "I'm never going to starve myself for a part… I want my body to look fit and strong, not thin and underfed."

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The "angelic" little girl in this awesome vintage snapshot clearly loved being in front the camera, a good omen for a career spent posing for pictures on beaches around the world. Only difference? Her bathing suits today are a bit more racy than this one-piece. What's your guess?

It's Alessandra Ambrosio, and no question, she's got one body-to-die for! To get her long, lean figure lingerie-ready, the hot mama of two works with both Brazil Butt lift founder Leandro Carvalho and Justin Gelband, as well as practicing Pilates, Capoeira, yoga, and indoor cycling. "It you have time, it's great to try and work out three to four times a week. If I have something big like the Victoria's Secret Fashion Show or a shoot, I try to work out daily," she says.

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America's favorite funny gal is looking pretty funny in this ‘80s pic (those #TBT's are supposed to be embarrassing, after all). In case you need another hint: The blonde beauty has mastered the art of interviewing while cracking jokes at the same time. Any guesses?

While her style has definitely changed, those beautiful blue eyes and flawless skin are exactly the same. Turns out those regular workouts with her trainer/nutritionist Mark MacDonald are doing the trick!

No stranger to sharing countless sexy pics on Instagram, this Throwback Thursday gothic snapshot was a total surprise. "I AM NINE," the now 40 fresh-faced supermodel wrote. Complete with multi-colored hair and black lipstick (along with that precious pout), who would have guessed the glam goddess had such a grungy side! So who is it?

Even after 20 years in the biz, Heidi Klum can still shock us! Something that's not surprising? Her ageless a-list figure, which she attributes to a diet rich with lean proteins and countless cardio/strength-training workouts with her trainer, David Kirsch.

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So little yet so chic! "I always did love #ALittleParty #Alittlepartyneverkillednobody", the singer wrote. From starring in the children's TV series Kids Incorporated to rocking the stage in front of millions of fans, this fierce female grew up to have a killer bod and a super handsome husband! Guess who?

Hello, Fergie! She's definitely dressing just as "Glamorous" today as she did when she was little, and with that fantastic figure, we'd want to show it off too! The sexy star says regular sweat sessions with her trainer Don ‘DB' Brooks and a healthy attitude are some of her secrets for staying trim and toned.

With or without those braces, it's easy to recognize this gorgeous face! The brunette bombshell went on to become one of the biggest supermodels in the biz. She tweeted, "#ThrowbackThursday: Backstage at a @Pepsi commercial where I get braces!" Who is she?

Cindy Crawford looks just as stunning 20 years later. What's her secret? Hiking, bike riding, and her Power Plate are just some of the things that keep the marvelous model in cover-ready shape.

There's nothing cuter than this childhood photo, to which the actress captioned, "My pigtail game was really legit." While she may seem super girly in this shot, don't be swayed; the pint-sized little lady grew into quite the athletic woman. The now 31-year-old actress climbed Mount Kilimanjaro in 2010 and was once named Esquire's "Sexiest Woman Alive." Can you guess who she is?

Jessica Biel grew up in Colorado, so she was always going snowboarding, hiking, and rafting with her parents. No wonder the brunette beauty still loves outdoor sweat sessions (especially running), along with grueling circuit workouts that mix cardio, strength, and plyometric training to keep her figure strong and sexy.

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This South African stunner is known for strutting the catwalks for Victoria's Secret, but by the looks of this priceless photo, she was just as graceful when she was little. Who do you think the beautiful ballerina might be?

VS Angel Candice Swanepoel makes jaws drop every time she steps onto the runway, thanks in part to intense workouts with her go-to-trainer, Justin Gelband. "I box and do a lot of resistance training at least three times a week," she says. "Your body is a machine, so you need to learn how to take care of it."

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Talk about a blast from the past! This "California Girl" sure was sweet. "Throwbackthursday in my sailor moon dress!" she wrote. Now the singer is all grown up and making music with her beau, John Mayer. Any guesses?

That's right, it's Katy Perry. So what's her body-sculpting secret? While on the road, the singer sticks to a ton of cardio—elliptical, running, and jumping rope.

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We're so happy this bubbly TV personality finally decided to jump on the #TBT bandwagon. "Halloween dance circa 84: With @JacquieAddeo. My first #throwbackthursday," she wrote. She may be rocking some super long hair and fierce fringe bangs, but we still recognize that smile. Guess who?

At the age of 37, Kelly Ripa discovered her passion for fitness and gave her abs, arms, and butt a total makeover. "For the first time, I have muscles!" she's said. Now 43, the media maven runs three to five miles every day and swears by Physique57 classes.

This old-school pic is pretty obvious, but we love seeing such an inspirational woman so candid! "Let's make sure every kid in America has a shot at a great education. #MakeCollegeAffordable #ThrowbackThursday," she wrote.

Michelle Obama looks just as beautiful today as she did in her 1985 Princeton graduation photo. The First Lady is an avid exerciser, squeezing in early-morning workouts in the White House. "Exercise is really important to me—it's therapeutic. So if I'm ever feeling tense or stressed or like I'm about to have a meltdown, I'll put on my iPod and head to the gym or out on a bike ride along Lake Michigan with the girls," she says.

This fit and fab female may be super serious about sports, but when she was little, it was all about fun. "#tbt being a 'clown,'" Can you guess who it is?

Fox Sports host Erin Andrews relies on simple toning moves with superlight weights to stay toned, a workout inspired by Physique57 classes. "I'm obsessed!" She says.

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Surely the tennis rackets are a dead giveaway, but can you guess who these famous sisters are? "Can you imagine two little girls from Compton got their picture with the president? #throwbackthursday #dreams #believe #americandream".

Venus and Serena Williams sure did make their dreams come true, thanks to hard work and dedication to their sport. "Luck has nothing to do with it, because I have spent many, many hours, countless hours, on the court working," Serena says.

Who knew this gorgeous brunette would look so pretty as a blonde? "Yep that's me!!! 6 years old lol #tbt #blonde."

Audrina Patridge is just as active today; for the SoCal native, it's always bikini season! Good thing the 28-year-old star is constantly in swimsuit-ready shape, due to shadowboxing workouts, Pilates, and resistance training. "If you eat healthy, you take care of yourself, you get your butt to the gym, even if you don't want to, you're going to feel better on the inside as well as the outside," she says.

Recognize this girl from her smize? "A British magazine snapped this pic pre photo shoot. Yup, this is how I dressed as a model! Nothin' wrong with flauntin' laid back overalls… fiercely of course ;-)" she wrote.

How does this former Victoria's Secret Angel remain so down-to-earth despite all the unrealistic body pressures of Hollywood? "I don't believe in diets," she says. And don't expect her show-stopping curves to ever get in the way of her success, either. "I get so much mail from young girls who say, ‘I look up to you, you're not as skinny as everyone else, I think you're beautiful.'"

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There's nothing better than our favorite stars sharing old childhood pics, and this one is no exception! "tbt costume idea! Except this wasn't a costume–my real self tryin to be a cheerleader at the ripe age of 10 #bangs #aquanet #1991" Know who this movie star is?

With two kids and a crazy busy career, keeping things balanced is extremely important for Jessica Alba. "Spending time with my kids kind of does take all the stress away, weirdly. I'm in the moment with them. They make me so happy, they're pure joy," she says.

Let's just say this actress was one very lucky girl! "tbt On set of #ThatNight w epic @JulietteLewis & then bf #BradPitt! Dad took this… ‘SO EMBARASSING, Dad…!' Lol." It's tough to take our eyes off Brad Pitt, but can you guess who this cute little lady is?

She's starred in Angel, Buffy the Vampire Slayer, and Bring It On, to name a few… so if you guessed Eliza Dushku, you got it right! The super-fit actress, who recently went vegan, has been training with Harley Pasternak for 10+ years.

It's hard not to smile when you see this precious photo. "#tbt Rocking a handmade dress and homemade haircut by my Mom," the former Dancing With the Stars contestant and TV personality wrote. So who is it?

The stunning 35-year-old brunette says she's in the best shape of her life, thanks to Krav Maga, Pilates, cardio, and strength training. "I don't have any routine that set because I don't obsess over anything," she says. "For me it's about health and relieving stress."

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Looks like this former first daughter is trying to teach her mom and dad a lesson in social media! "Twitter lesson Mom & Dad: Thursdays are an excuse 4 #TBT. This is 1 of my favorites!" It might just be one of our faves too. So can you guess who it is?

The best part of Chelsea Clinton's #TBT post? Her dad, former President Bill Clinton, tweeted back, writing, "Even then you were a great teacher."