At 20, Miley Cyrus has been working in show business for more than a decade. The singer/actress has gone from being a fresh-faced preteen to a platinum blond vixen who scandalized the MTV VMAs in 2013 with her "twerking." 
Selena Gomez's appearance hasn't changed dramatically since she starred on the Disney Channel's "Wizards of Waverly Place" in 2007, but her work sure has. Now 21, Gomez has stretched herself with more mature content, such as the risqué movie "Spring Breakers" and her suggestive new single, "Come and Get It." 
Remember Derek Boyd, the ace "Yankee Doodle Dandy" singer on "Full House"? That was Blake McIver (formerly Blake McIver Ewing), whom you may also remember as Waldo from 1994's "The Little Rascals." These days, 28-year-old McIver is definitely more adult, as his Instagram account shows. The one-time child star told RumorFix that he's been working as a go-go boy in Los Angeles and is preparing to release his first album on Tuesday, November 5. 
Alyssa Milano, who starred as a pre-teen on the '80s series "Who's The Boss?," thinks talent is one factor that helps a child star safely transition into more adult roles. 
Seven years ago, Jaden Smith was a baby-faced child star appearing with his dad Will in 2006's "The Pursuit of Happyness." Although he's once again starring with his father in this summer's "After Earth," teenaged Jaden isn't a kid anymore. 
Along with her older brother Jaden, 12-year-old Willow Smith has blossomed since she first appeared alongside dad Will in his 2007 film, "I Am Legend." The actress and singer showed a more mature look this spring at the May 2013 premiere of "After Earth." 
Vanessa Hudgens came to fame as a Disney Channel star in 2006 but soon stepped away from her wholesome "High School Musical" roots. This year, the 24-year-old is appearing in more adult projects, such as "Spring Breakers" and "Machete Kills." 
It's still hard to believe that Rudy Huxtable is now 34 years old. Keshia Knight Pulliam, the actress who played Rudy on "The Cosby Show" from 1984 to 1992, grew up on TV but acted sporadically since then. This year, she took a dive into reality TV with ABC's competitive diving show, "Splash." 
Macaulay Culkin turned a scream and an exaggerated expression into a blockbuster movie franchise when he starred in 1990's "Home Alone" at the age of 10. He went on to co-star with in 1991's "My Girl," but has in later years not been a huge fan of being on camera. In April, he ripped into paparazzi in the UK for trying to take his photo. 
Along with Knight Pulliam, Raven-Symone is one of the most recognizable child stars, thanks to her work on the long-running "Cosby Show" and her subsequent career on the Disney Channel. The actress has been in the business since the age of 3, and most recently appeared on ABC Family's "State of Georgia." 
"Mad Men" fans have watched Kiernan Shipka grow up as Sally, the daughter of protagonist Don Draper. Having starred on the series since she was 7, Shipka's gone from being a little ballerina with a lisp to a teen girl with enviable poise over the series' six seasons. 
One minute, Abigail Breslin was a 10-year-old "Little Miss Sunshine," and the next thing we know, she's flashing her bra in 2011's "New Year's Eve." The now 17-year-old is grownup enough to take on the older sister role, as she will in the November release, "Ender's Game." 
Along with Vanessa Hudgens, Zac Efron was just a teen when he became famous with Disney's "High School Musical." Now 25, Efron caters to audiences well past high school, such as his turn in Lee Daniels' 2012 film, "The Paperboy." 
Mary-Kate and Ashley Olsen have been in the entertainment industry since they were literally in diapers -- the pair took turns playing the youngest daughter of the Tanner clan, Michelle, on "Full House" from 1987 to 1995. They went on to star in their own movies, but these days the twins are better known for their fashion lines, Elizabeth and James and The Row. 
Best known for his role as Renee Zellweger's cute-beyond-words son in 1996's "Jerry Maguire," Jonathan Lipnicki is now old enough to play Zellweger's love interest. According to IMDb, the 22-year-old has a dramatic film arriving this year starring Christopher Mintz-Plasse called "Tag." 
Chloë Grace Moretz was a "Kick-Ass" actress even as a kid, starring in movies like "The Amityville Horror" at age 8. Now 16, Moretz has ditched the Shirley Temple curls but not her action moves -- the star will appear in the sequel to 2010's "Kick-Ass" this August. 
Dakota Fanning has appeared in so many movies and TV shows since her career's launch around age 6 that we could put together her baby book. Now 19, Fanning is not only an acclaimed actress, but also a high school graduate. 
Daniel Radcliffe's development has been watched by millions as he came of age in the "Harry Potter" movie franchise, which launched when he was 12. By 2007, Radcliffe was ready to show how grown-up he'd become and starred in "Equus" in London -- a stage production that required some nudity. 
Along with her "Harry Potter" series co-star Radcliffe, Emma Watson's racking up proof that she's not little Hermione anymore. The 23-year-old actress plays a thief in this summer's "Bling Ring," and an ax-carrying marauder in Seth Rogen's comedy, "This Is The End." 
Angus T. Jones wasn't yet 10 when "Two and a Half Men" first premiered on CBS in September 2003. A decade later, the now adult actor is ready to break away from the sitcom -- one that he's publicly said he finds distasteful -- and won't be a regular star on the 11th season this fall. 
Justin Bieber is only 19, and, according to his mentor Usher, is still in the midst of growing up. But between the tattoos, the ab workouts and those reckless driving accusations, Biebs is not the same "Baby" singer we met in 2009. 
Amanda Bynes began working at 10, and by the time she was 14 had starring roles on two Nickelodeon shows. Yet around age 24, Bynes ceased her steady work schedule and claimed she was "retired." Lately, that "retirement" has translated into troubling run-ins with the law. 
Lindsay Lohan showed acting prowess at 12 when she played a set of identical twins in the 1998 remake of "The Parent Trap." Lohan went on to star in movies like "Freaky Friday" (2003) and "Mean Girls" (2004), but her tumultuous private life soon interfered with her career. 
Anna Chlumsky became a star at age 11 thanks to her role in 1991's "My Girl." After sporadic appearances on TV, the now 32-year-old, who's expecting her first child this year, has landed a hit comedy with HBO's "Veep." 
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- This year, a number of teen stars tried to transition to adult fame
- Selena Gomez did a risque movie, Miley Cyrus did risque everything
- Justin Bieber weathered 12 months of rough seas before joking that he's "retiring"
- Ariana Grande managed to gain adult acclaim without much scandal
(CNN) -- After the year he's had, no one could blame Justin Bieber if he really does want to retire.
The 19-year-old has spent the past 12 months stuck in a public storm of negative press, bad decisions, ailments and misfires, all while trying to scrub off the sheen of his tween popularity. With a barely there 'stache lingering on his upper lip, the pop star has spent 2013 attempting to assert his manhood and find a bridge over to the adult side of the pop world -- all without completely disregarding the persona or the young fans that helped him become a star in the first place.
It's a delicate and practically impossible balance, a tightrope that Bieber, his ex-girlfriend Selena Gomez, and some cohorts like Miley Cyrus and Ariana Grande have all walked this year to varying degrees of success.
Gomez, now 21, has long shed the role that made her famous with younger crowds, that of Alex Russo on the Disney Channel's "Wizards of Waverly Place." Even as she grew more recognizable thanks to Disney's marketing prowess, Gomez was never solely definable by the series -- there were departures for albums with her band, Selena Gomez & the Scene, and movies like 2011's "Monte Carlo."
But even with those efforts, Gomez began 2013 with a still-intact image as a young adult star. Although she's in the same age group as her BFF Taylor Swift, Gomez didn't enjoy the same broad demographic appeal.
Then March brought Harmony Korine's "Spring Breakers," a sly project aimed directly at the nexus of emerging womanhood. Alongside one actress who's already come out on the other side of the teen star transition, Vanessa Hudgens, and one who stands on the cusp, Ashley Benson of "Pretty Little Liars," Gomez put on a string bikini and struck the requisite provocative poses.
It was the kind of risque territory that legions of adolescent stars before her have eagerly walked into, because it always sends a crystal clear message: I'm not a kid anymore, and it's time you started treating me like an adult artist.
"The transition's weird and it's awkward," Gomez told CNN of trying to mature in the spotlight with projects like "Spring Breakers." "You don't really know what the right and wrong thing to do is when you do it, but you can just do projects that you're really passionate about and this was something that I was definitely excited to be a part of."
Go back roughly 10 years and you would have heard something similar from a then 21-year-old Britney Spears, who caused her own uproar when she kissed Madonna at the MTV Video Music Awards. "Honestly, it's about me just performing and expressing myself," she told CNN of the backlash to her "adult" behavior, which at the time left some, including this network, questioning how the change in the former Mouseketeer's image would affect her young fans.
Although Spears herself perhaps put it best when she said, "I'm not a girl; not yet a woman," she wasn't the only one struggling. Around the same time, Christina Aguilera was "Dirrtying" up her reputation with chaps and explicit lyrics, and Spears' ex-boyfriend, Justin Timberlake, was in the midst of reforming himself from a boy band member to bonafide pop star by promising to have his love interest "naked by the end of this song." He took his freshly cultivated sex appeal a step too far at the 2004 Super Bowl halftime show, when he assisted in Janet Jackson's "wardrobe malfunction."
But if there's any comfort to be had for today's young celebrities, it's that each of those singers has been able to move past that "weird and awkward" phase Gomez described. Bieber especially is probably relieved to see that Timberlake survived that enormous scandal to dominate the charts years later with "The 20/20 Experience."
In Bieber's case, he can end the year satisfied that he has stretched himself enough artistically to gain positive attention for an older sound, even if the world isn't quite ready to accept the adult artist he's becoming. Bieber never had to contend with being a part of what's referred to as the "Disney machine," but he did become very famous very quickly at a very young age. Chances are it's still difficult for the average adult older than 21 to name a Bieber hit that isn't "Baby" or "One Less Lonely Girl," two songs that helped launch his career when he was 15.
So when he says he plans to retire -- which he's done repeatedly in the weeks leading up to the end of the year in what may or may not be an extended prank that his rep won't comment on -- perhaps it's more likely that he doesn't want to quit singing but just wants to retire that old, floppy-haired image. In some ways he's done that, even if it was inadvertently, with the constant topless photos he's shared, his altercations with paparazzi, and the salacious rumors that dogged the South American stretch of his tour this year. The music he's created -- sultry songs about love, heartbreak and pillow talk, with a suggestive video to match -- have only further shown his willingness to leave the kids' table.
One of his tour companions, Ariana Grande, has shown the same desire in a much more subtle way. At 20, Grande is best known to the under-18s as Nickelodeon's Cat Valentine on the network's "Victorious" and "Sam & Cat." But with the release of her debut album, "Yours Truly," in August, Grande proved she's ready and capable to handle an older audience.
She did that not with the usual scandals but with a No. 1 album that gained her entrée to larger platforms, such as a performance at the 2013 American Music Awards that earned praise from the likes of Lady Gaga and Kelly Clarkson.
The Disney Channel says it's aware of the rocky terrain that lies ahead for kids who want a career beyond the network's family-friendly realm.
According to Patti McTeague, the senior vice president of Kids Communications for Disney ABC Television Group, the Disney Channel doesn't try to "control or dictate an actor's image" while they're working with the company, although they do offer a "Talent 101" orientation to help the budding star prepare for what's ahead.
Outside that guidance, though, McTeague said in a statement that "the talent has the control over their career; we want them to be obligated to the art of their craft not obligated to us. We recognize we are working with young people at a transition in their personal development -- aka, teenagers -- and we trust parents of employed minors to support and guide their kids."
And, when the time comes that said talent wants to move on from Disney, "we don't try to slow the hands of time," she continued. "Hopefully, these young actors continue to follow their dreams, explore roles that make sense for them and take their career to the next level."
For at least one former Disney name, Miley Cyrus, making that leap to a new level meant burning down that Mouse House image altogether.
The 21-year-old has been trying to liberate herself from her "Hannah Montana" past for years, but it wasn't until 2013 when she was fully able to, in her own words, kill off the character who made her famous.
With a new aesthetic, a discovered fondness for suggestive photography, an unfiltered Twitter account and a bold approach to stealing the limelight at each and every awards show that had her on the bill, Cyrus cheerfully let her prior kid-friendly image go up in flames. Although the public stood by and watched like a collective set of exasperated parents, Cyrus is entering 2014 with her mission accomplished. The shock value of seeing a singer and actress who was once the idol of nearly every 9-year-old in America swing naked from a wrecking ball has sunk in; there's little, if anything else, she needs to do to assert her adult independence.
The transition, for Cyrus at least, is complete.
