Transitioning from a child star to a teen star can be tough if you undergo a growth spurt and go from cuddly and cute to tall and gangly in just a few months. It's easiest if the actor plays a character on a long running show where the audience can actually watch them mature over several years so the physical changes aren't so jarring. And even if the changes are natural, if they don't coincide with the script – like growing 6 inches in 3 months or hardly growing taller at all – actors are sometimes replaced for aesthetic reasons.
Even more difficult is the transition from teen star to adult star. Puberty is typically rough for everyone with the spiking hormones, uncontrollable physical transformations (for better or worse) and self-esteem issues. Imagine trying to find a job based on physical appearance and demeanor while turning 20, and facing casting directors who can't decide if you are better cast as someone older or younger than your actual age.
These actors have proven their talents could withstand the test of time. Some have had rougher terrain to navigate than others to make the transition but have nonetheless prevailed.
21 Joseph Gordon-Levitt
Although he had a few roles as a child, most notably in the award winning movie A River Runs Through It. Gordon-Levitt's first recurring television part was on Roseanne from 1993 to 1995 and then in 1996, at age 15, he became a star as part of the ensemble cast on 3rd Rock From the Sun. He also co-starred in Angels in the Outfield , The Juror, and 10 Things I Hate About You (1999). Since 3rd Rock ended in 2001, Gordon-Levitt has had major roles or starred in over 20 movies including such hits as (500) Days of Summer, Inception, 50/50, The Dark Knight Rises, Looper, Lincoln and Don Jon.
20 Shia LaBeouf
Before landing a key role in the Disney Channel series Even Stevens in 2000 at age 14, LaBeouf had a string of supporting roles on popular TV shows including Suddenly Susan, ER, Touched by an Angel, Freaks and Geeks, and The X-Files. In 2003, he made his film debut in Holes and has since starred in hits like Indiana Jones and the Kingdom of the Crystal Skull, Wall Street 2 and both Transformers movies.
19 Leonardo DiCaprio
At the tender age of 16, baby-faced DiCaprio charmed audiences with memorable parts on an unsuccessful rendition of Parenthood on NBC in 1990 as well as a recurring role on the classic comedy Growing Pains. Those parts led to leads in successful movies like This Boy's Life, What's Eating Gilbert Grape? and The Basketball Diaries. DiCaprio's been on a roll since then, proving he's much more than a pretty face in blockbusters directed by luminaries including Christopher Nolan, Quentin Tarantino and Martin Scorsese.
18 Christina Applegate
Although she had steady work in TV and film from the age of 10, Applegate's big break came when she was 16 and was cast as Kelly Bundy on the irreverent sitcom Married…with Children. She was 26 when the show was cancelled and the next year Applegate landed the lead in the TV comedy Jesse. Since then she's starred in two more TV comedies and acted in many TV series and movies, including both Anchorman movies.
17 Zac Efron
16 Fred Savage
He was only 12 when his career took off playing the precocious yet precious Kevin Arnold on the TV hit The Wonder Years but by the time the show went off the air, Savage was 17 and anxious to play adult roles. He's since played a variety of roles on television, provided voices for several animated characters and starred in the TV comedy Working for 2 years. Savage's directing credits include numerous episodes of 2 Broke Girls, Modern Family, It's Always Sunny In Philadelphia and Happy Endings.
15 Jessica Biel
As Mary Camden on the TV show 7th Heaven, Biel grew up in the role at the same time she was emerging into womanhood over the 10 years she played the part from age 14 through 24. Her career has been on the rise ever since in movies including Total Recall, Hitchcock, Valentine's Day and New Year's Eve.
14 Ryan Gosling
After cutting his acting teeth on revival of The Mickey Mouse Club, Gosling had a smattering of supportive roles on TV and by his 17th birthday was starring in the short-lived TV series Breaker High. He soon made the big leap to movies and made significant contributions to the success of such hits as Crazy, Stupid Love, Remember the Titans, Drive, Murder by Numbers and The Notebook.
13 Keri Russell
As a teenager Russell was in the cast of Malibu Shores and 2 years later starred in her own show, Felicity, which had a 4 year run. Over the next 8 years she appeared in a mixture of dramatic and comedic parts in TV and movies, garnering critical acclaim for her starring role in the movie Waitress. She currently stars in the gripping Academy Award winning TV drama The Americans for which she was Emmy nominated for Best Actress in a Television Series.
12 Johnny Galecki
11 Sarah Michelle Gellar
Soap operas launched Gellar's career. At 15 she starred in Swans Crossing, a soap aimed at teenagers and the next year, in 1993, landed the prized role of Kendall, Erica Kane's long lost, troubled daughter on the iconic soap opera All My Children. But the title role in the quirky TV show Buffy the Vampire Slayer is what pushed her over the top into bona fide stardom in 1996. Since then Gellar has appeared in a string of movies and TV shows including sharing the bill with the late Robin Williams in the TV comedy The Crazy Ones.
10 Sarah Jessica Parker
After acting on stage for several years, including a successful Broadway run as Annie, Sarah Jessica Parker was 17 when she gained recognition for her role in TV's Square Pegs. The show was only on a season but that exposure led to roles in Footloose, Girls Just Wanna Have Fun and Flight of the Navigator. Parker has appeared in over 50 TV shows and movies, with her portrayal of Carrie Bradshaw in Sex and the City being most memorable.
9 Neil Patrick Harris
Although he'd been acting in school plays since elementary school, Neil Patrick Harris' professional career was launched with a role in the Whoopi Goldberg movie Clara's Heart when he was 15. At sweet 16, he shot to stardom as a child prodigy doctor in the TV sitcom Doogie Howser, M.D. Harris spent 8 years as a ensemble cast star on How I Met Your Mother and continues to act on stage and screen, with critical acclaim for hosting major awards shows such as the Emmys and Grammys.
8 Hayden Panettiere
7 Mayim Bialik
By the time she was 15, Mayim Bialik had already starred in the TV movie Blossom and in her own TV series Molloy. The TV series Blossom came next and had a 5-year run. Bialik appeared in about 15 different shows over the next 10 years and then took some time off to start a family. She's currently one of the stars of one of TVs biggest hits, The Big Bang Theory.
6 Joshua Jackson
For many teenyboppers, Joshua Jackson was their first crush when he appeared as a teenager in all three Mighty Ducks movies. He made several other teen-oriented movies before looming large as Pacey on the WB mega hit Dawson's Creek, which ran for six seasons. More recently, Jackson starred for six seasons on the sci-fi thriller Fringe and he just began playing his steamiest part to date as the star of Showtime's The Affair.
5 Anna Chlumsky
Although she was just 11 years old when she stole hearts opposite Macaulay Culkin in My Girl, Anna Chlumsky continued acting in a string of supporting roles in TV and movies. At age 18, she left acting to attend college and then started a family. Her part in In the Loop got high marks that led to her current role on HBO's Veep, which earned her an Emmy nomination.
4 Mila Kunis
By the age of 14, Kunis had over 20 acting credits including a recurring role on7th Heaven. But her most memorable TV role was one of the leading parts on the hit sitcom That '70s Show that began when she was 15 and lasted eight seasons. Soon she was showcasing her talents in box office successes such as Ted, Friends With Benefits and Black Swan.
3 Claire Danes
Although she was just 15 when My So-Called Life brought her worldwide acclaim, it was a pivotal role that launched her movie career, even though the quirky teen angst dramedy only lasted one season. It so happens her return to TV as the star of the biographical HBO movie Temple Grandin gained her the most acclaim of her career, an Emmy. Claire Danes is now in the fourth season starring in the Showtime winner Homeland.
2 Jennifer Love Hewitt
Jennifer Love Hewitt began acting at the tender age of 10 and had four TV series and a slew of movies under her belt before she hit it big with a lead part on TV's Party of Five. Although her spinoff of that show flopped, Hewitt has since had success in several TV dramas including The Ghost Whisperer, The Client List and Criminal Minds.
1 Alyssa Milano
Before the age of 12, Milano had performed on stage and appeared in four movies and three made-for-TV movies. But just as she was crossing over to her teens, she landed the part of Samantha Micelli, the daughter of Tony Danza's character on Who's The Boss?, the role that really kick started her acting career. That show led to leading parts in Commando, Melrose Place, Charmed, My Name is Earl and, most recently, Mistresses.