Once upon a time, a skinny white boy from Memphis, Tenn., wrapped a bandanna around his wild 'fro, indulged in aerobic dance steps and, with his four group mates, strapped on a harness to fly over stadiums of hyperventilating pre-teens.

The boy was always the favorite, edging in front of his pals to beat box on "Pop," show off his falsetto on "Gone" and, as we've now learned, frequently inhale.

He was also the first to wave bye bye (bye) to his less talented friends -- with the exception of JC Chasez.

Not many expected his 2002 solo debut to be anything more than passable Top 40 pop, an unspectacular footnote in the career of yet another vapid pop idol.

But here is where that story ends.

Justin Timberlake's "Justified" turned out to be a crafty collection of meaty R&B-flavored pop. The 13 songs on the album, all of which he co-wrote, sneaked in dribbles of Michael Jackson's "Off the Wall" and Prince in his most commercial phases.

"Justified" became an instant hit, selling more than 3½ million copies in the United States. Timberlake was crowned the burgeoning king of pop and the boy became a man.

That man, all of 25 years old now, ushered in the next phase of his domination of smart pop music with a sold-out-in-eight-minutes show on Friday at the 9:30 Club in D.C.

Designed to hype his Sept. 12 sophomore release, "FutureSex/LoveSounds," this tour of only 13 dates in teeny venues proved with one simple mandate that Timberlake is all about being an adult now -- if you weren't 18 or older, you didn't get in. Take that, you glow-stick waving tweens who are only interested in Timberlake's lopsided smile and '80s-inspired dance moves, such as the Robot. (Go Justin! Go Justin!)

His vigorous 90-minute set began somewhat amusingly, as the classical strains of Prokofiev's "Peter and the Wolf" melded into the dark strains of "Cry Me a River," his middle finger of a song to his ex, Britney Spears. Seated behind an electric piano, waving to and cueing the crackerjack 11-piece ensemble crammed behind him, Timberlake appeared to summon the spirit of Ray Charles as he bobbed and absorbed the thick music.

But let's not get ahead of ourselves, big guy.

Timberlake is aching to be taken seriously as an artist -- he occasionally offered some gliding dance steps, but no pyro, production numbers or even costume changes. Still, even dressed up in a natty dark suit and tie -- he's definitely bringing classy back -- Timberlake acts his age all too often.

Before playing the first of a handful of new tunes, he told the 1,200-plus, 90 percent female crowd, "I hope you like them, but, if not, well, [blank] you."

Of course it was said with a cheeky grin, but Timberlake's confidence in himself and his music borders on smug, an inevitable detraction from his worthwhile creations.

Of that new material, "My Love" is the strongest of the bunch and, with its charming rhythmic changes and a wonky guitar riff squirting '70s disco infectiousness, would have be an infinitely better lead single than the monotonous, migraineinducing "SexyBack."

Another newbie, "Till the End of Time," is a standard love ballad straight out of the Janet Jackson songbook, a blah, chimes-infested droner that nonetheless had the audience swaying their arms in the air at Timberlake's command.

That, of course, is the larger point here. Even at his most mundane, Timberlake is a star, capable of inciting a frenzy by merely tacking on a snippet of Nirvana's "Smells Like Teen Spirit" at the end of a superbly tight and choppy "Like I Love You." The purpose of the Nirvana nod might have been an attempt at rock cred (leave it alone, bud), but more likely a lazy method of provoking the crowd and band to bounce simultaneously in a thundering musical climax.

As a showman, Timberlake didn't need to do much more to keep this group enthralled than quietly remove layers of his suit, unbutton the top of his shirt and occasionally thrust his pelvis and rear end as provocative come-ons. When he tossed the remains of his water bottle on the front rows during a funky "Rock Your Body" which nicely incorporated the bass line of Chic's "Good Times" -- you would have thought those droplets morphed into $100 bills, given the ridiculous reaction.

Throughout the night, Timberlake's flexible voice ably segued from searing falsetto to soul growl, which made the show-closing appearance of the vocally subpar "SexyBack" a drag.

True, given its droning beat and minimal lyrics, the song thrived in a club environment, especially with the added adrenaline provided by surprise guest Timbaland, the Virginia Beach mastermind who produced much of Timberlake's album and is responsible for the least annoying parts of "SexyBack."

The twosome proved their muscularity by turning out another impromptu version of the song, done D.C. go-go style, another impressive check on Timberlake's list of music knowledge.

He wants to claim that king of pop crown, no doubt -- and maybe some day he will. But at this point, Timberlake, even all grown up, is still just a prince.