These Pictures of a Young Joseph Gordon-Levitt Will Take You Right Back to Your Teen Years

An adorably serious 20-year-old Joseph Gordon-Levitt (yes, believe it or not, he's 20 here) attended the E! Party during the 2001 Sundance Film Festival in Park City, UT.

During 2001's Sundance Film Festival, he also had his portrait taken for Manic, which he starred in opposite his future 500 Days of Summer costar Zooey Deschanel.

He donned a sweet pair of glasses for the Treasure Planet premiere at the Cinerama Dome in Hollywood in 2002.

He even looked cute in his puffy red jacket and messenger bag when he arrived for the 25th Hour world premiere at the Ziegfeld Theater in New York.

Not much had changed by the premiere of XX/XY at the 8th Annual Gen Art Film Festival's Closing Night Gala at Loews Astor Plaza in New York, except the color of his puffy jacket.

He was his usual charming self at the New York premiere of Manic at Village Cinema #7 in New York, over two years after it was first shown at Sundance in 2001.

For the Amelia Toro Fall 2003 Fashion Show at Avalon Hotel in Beverly Hills, JGL showed up in a sporty varsity jacket.

He grew out his hair (and looked very much like his old 3rd Rock From the Sun character, Tommy) for the Point and Shoot premiere at the 3rd Annual Tribeca Film Festival.

And he completed his nerdy-chic look with a pair of glasses and a backpack for the Thunderbirds screening at the Tribeca Film Festival.

By the time the 2004 Venice Film Festival rolled around, JGL had really blossomed from boy to man (and it only took 23 years to happen).

For the Mysterious Skin premiere at the Venice Film Festival, he wore a tie and everything.

Just look how cute his festival portrait turned out!

At the Silver City party during the Toronto International Film Festival, JGL arrived with his trusty messenger bag and looking way too young to be holding that adult beverage.

But during the Hollywood Foreign Press Association Toronto Film Festival party, he was all smiles and back in a tie and jacket.

For the Brick premiere at the 2005 Sundance Film Festival, his adorable argyle sweater also made a premiere (and his long hair made a comeback).

Seriously, that sweater is everything.

Though he still couldn't find a suit that fit him right by 2005, his sweet smile at the 31st American Film Festival of Deauville made his outfit forgivable.

By the time the Los Angeles Shadowboxer premiere at Arclight Theatre rolled around in 2006, JGL had clipped his hair and was finally starting to look like the actor we now know and love.

Only he could make an arm sling look cool, which he wore along with a smart suit to the Los Angeles premiere of The Lookout at the Egyptian Theater.

At Remember the Daze (originally titled The Beautiful Ordinary) world premiere at Landmark's Regent Theater in Westwood, CA, he was looking more manly than ever.

He even showed up with — gasp! — facial hair for the Los Angeles Stop-Loss premiere at the Directors Guild of America in Hollywood.

At Hollywood Life Magazine's 10th Annual Young Hollywood Awards at the Avalon, it seemed as though 27-year-old JGL had finally found a style and a haircut that really worked.

And when 500 Days of Summer premiered during the Sundance Film Festival at Eccles Theater, Joseph-Gordon Levitt officially had our hearts.