We look back at some of our favourite celebs in their teenage years - and how much they've come on since!

Since we posted a #throwback video of a 15-year-old Justin Bieber singing Where Are You Now, we’ve not been able to stop watching it on a loop. He’s just so young. 15 years young!

And, when you compare the shiny-haired slip of a lad that appears in the video to the Biebs we’ve come to know and love (and sometimes, just sometimes, despair of) in recent years, the difference really is quite jaw-dropping.

Which go us thinking about how some of our other favourite celebs have changed since the magical age that is 15 (which, we can pretty much all agree, is typically characterised by dubious hairstyles and dodgy outfit choices).

Take, for example, Justin’s ex-girlfriend, Selena Gomez. Her star was only just rising back in 2007, when 15-year-old Selena was appearing on Disney show The Wizards of Waverly Place. Fast-forward 8 years and she’s blossomed into a super-sophisticated beauty.

Fellow child star Miley Cyrus is another one who’s changed massively since her teenage years, swapping country-girl checked shirts and cowboy boots for barely-there outfits and her favourite accessory: her big ol’ tongue.

Then there’s the Jenner sisters. It’s just three years since Kylie was 15, but what a difference those three years have made. Gone is the cute-as-a-button, slightly awkward young’un and in her place is a bona fide bombshell, whilst older sister Kendall has swapped her role as head cheerleader for head of the Fashion Week model brigade.

Elsewhere, actress Emma Watson was already onto her fourth Harry Potter film by the age of 15 – although her red carpet wardrobe hadn’t quite caught up with her megastar status (see: the questionable headband pictured in the gallery above). But now, at the age of 25, Emma is a bona fide fashion star, topping countless best dressed lists and wowing with every red carpet outing.

And if you think Emma’s early CV is impressive, what about the Olsen twins? Mary-Kate and Ashley had racked up a whopping THIRTEEN movies and a long-running TV series by the time pimples and growing pains kicked in. Since then, they’ve swapped the cute double act for a serious career as fashion designers.

LeAnn Rimes had not one, but two Grammy Awards by the age of 15 – but sadly not a hairstylist who warned her against the horrors of a perm. Eighteen years on and the singer has thankfully ditched the super tight curls in favour of a more relaxed look.

And finally, with the picture that will surely give hope to awkward teens everywhere, we come to Justin Timberlake. N*Sync were just starting out when JT was a fresh-faced 15 year old – with dyed-blonde curls and a penchant for shiny silver jackets to boot. The fact that he’s now one of the world’s hottest hunks really is a testament to the benefit of time!

Check out all the pictures in the gallery above!