Because of the weather, a freak blizzard in late April that dumped a foot of snow on the streets of Colorado Springs, Colorado, Michael Phelps has ditched his usual flip-flops and boardshorts for a pair of scuffed Pumas and a rumpled tracksuit. With his backpack, iPod, and greasy Tigers cap, he could be any kid slouching around a college quad, another shaggy white boy banging hip-hop. But this isn't a college quad; it's the U.S. Olympic Training Center, and the kid in those baggy sweats is a coil of forward motion that might just be the greatest athlete alive.

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Upstairs, on the deck of the 50-meter pool, he reappears wearing the navy trunks of the U.S. national team. The first thing you notice, besides the Olympic tattoo notched on the blade of his right hip, is that Phelps's chest and legs don't match. He has the long torso and hulking wingspan of a six-nine power forward but the low waist and thighs of a six-foot tailback. This genetic mashup serves him well. In the water, where your lower body weighs you down, Phelps is unnaturally aerodynamic, a broad reed skimming the surface. He is also double-jointed, and his extremities flex steeply to pull him through the chop. His rarest gift, however, can't be seen on land: Phelps doesn't tire in the water. He was born with, and has since refined, the power to rebound quickly. His recovery rate, as measured by lactate levels, outstrips those of his opponents, which is why he's able to compete in three events on the same day, by far the most in the world.

There are two groups of collegiate- and national-level swimmers on hand today in the center's glittering pool, and though many of the men are wearing the blue-and-gold caps of Phelps's Club Wolverine, I have no trouble picking him out. Even warming up he seems to knife along as if carving a sheet of ice, each stroke a duplicate of the one before it, at 3,000 and then 5,000 meters. He is here, after a history-making eight-day blitz at the World Championships in Melbourne, Australia, in March – seven gold medals, five world records, widespread acclamation as the greatest swimmer ever – to resume hard training under his longtime coach, the brilliant and combustible Bob Bowman. Things are off to a workmanlike start when suddenly Bowman blows his whistle.

"Out of the pool!" he barks and points to the corner; the group of swimmers herd there, eyes cast down. "You're going to stand here, all of you, till you can tell me why you've decided to waste my time. I flew 14 hours to be here to try to make you better, but none of you seem to want that today.

The rant goes on in a lower voice. No one says anything for 10 minutes. Ordered back in, they swim a grueling hour, then they all climb out of the pool with arms like anvils. All, that is, but Phelps, who saunters past with the smirk of a kid who swiped his teacher's lunch.

"That was me," he says, referring to Bowman's outburst. "He caught me playing tag while I swam my laps."

Does that happen often, the yelling and such?

"Oh, that wasn't yelling. You should see him angry."

After practice I join Phelps for a prodigious dinner at the Olympic Center's dining hall. His intake is legendary. I watch him plow through twin servings of brisket, plus pasta, salad, and fries. Between bites he fields questions about the drive needed to swim nearly 50 miles a week at two-a-day sessions and not take a day off for many months, to swim Christmas and birthdays year after year from the time he was 12 years old. "I've always been taught to have a plan and stick to it," he says. "To swim my race even in practice."

It's a careful answer to a tiresome question, and reflective of the young man he is: locked-down, deliberate, and almost absurdly single-minded. But here and there are hints of that kid in the pool, the one who played tag to rile his coach: the BlackBerry that keeps beeping with texts from childhood friends; the eyes that light up when he talks about Michael Jordan, whom he worshipped as a boy and still does. It's the bearing of a guy who isn't fully formed, who grew up in a pool, facedown in the water, and isn't entirely sure who he wants to be. From age 15, when he became the youngest male in 68 years to make the U.S. Olympic swim team, he has created huge hopes and then somehow surpassed them. To deliver on such promise is a rare enough thing. But he did so after a difficult and heartsore childhood – a neurological impairment, a father who walked out on him, years of being bullied and teased – and after very nearly caving to his short-fuse temper and quitting the sport he loved twice.

Unless he blows up and suddenly quits again, Phelps will go on with twice daily sessions from now until next August's Beijing Olympics, using head paddles and kickboards as he swims.

"I've done that so long," he says, "that it just feels normal, and the rest of the other stuff will have to wait." That other stuff – the group of friends he seldom sees, the mother and two sisters he talks to often and the father he's rarely in touch with, the townhouse he bought in Ann Arbor, Michigan – all of that will have to wait. He has history to make, and there's no other way. In swimming, the price of greatness is extreme.

We live, these days, in an age of wonders, a sportsman's belle epoque of the newly possible: quarterbacks outrunning fleet free safeties and throwing pinpoint spirals 60 yards; shortstops mashing fastballs into the upper decks, then ranging to the hole for the long throw to first – today's banal brilliance would have looked like science fiction to viewers just a decade ago. We all know the litany of the locker room now: Better training plus top nutrition plus a chemist's magic equals bigger, faster, stronger, and, above all, richer. But if that helps explain the Michael Vicks and Miguel Tejadas, then how do you account for the truly prodigious, the athlete who far separates himself from his fellow genetic and pneumatic winners?

Michael Phelps is a member of a masters class unseen in the annals of sport, men who rule their respective games and have made us rethink the limits of physical endeavor. Like Roger Federer or Tiger Woods, Phelps has a claim to being the best of all time at what he does, reducing most meets to races against himself and his own record times in events. He doesn't just win; he destroys opponents, taking events by whole seconds, not hundredths. He doesn't just break records; he makes mockeries of them, beating the red-line graphic that TV imposes by a body length or more. And like Woods and Federer, he's a generalist who's better at almost everything than his foes.

Look at the Worlds in Australia. But for an odd slip (one of his teammates dove early, disqualifying the team in the medley relay) he'd have passed Mark Spitz's record of seven gold medals, set in the 1972 Munich Olympics. (Phelps himself won six at the Athens Olympics in '04, and swam six seconds faster in the 200-meter butterfly than Spitz did when winning his gold.) His marks are so daunting that other medal winners suddenly decide to switch events. Pieter van den Hoogenband, the Dutch swimmer who won gold medals in the '00 Olympics and silver in '04 in the 200-meter freestyle, may drop the event in Beijing next summer after Phelps swam two seconds faster than he did in Melbourne. The freestyle, it bears noting, was one of Phelps's weaker events till he suddenly lapped the world at it in March.

Indeed, if Phelps has a problem now, it is finding a rival in any of his various events. Ian Crocker, a University of Texas grad who holds the record in the 100-meter butterfly, beat Phelps in world meets in 2003 and '05. After the loss in '03 Phelps put Crocker's picture on his wall to remind himself how much he despised losing, then went on to beat him in the Athens Games and again this year in the Worlds.

"I do have guys who can beat me in events, and Ian's one of them," he allows. Pressed to name another he mentions Ryan Lochte, the 200-meter backstroke record holder and medley swimmer who has challenged but never actually beaten Phelps in a race.

Like Federer, who can't win on clay, and Woods, whose stroke has failed him over prolonged stretches, Phelps has imperfections. His turns at the wall can be less than stellar, and his dives off the blocks can be ugly affairs, almost belly flops. Still, these glitches haven't held him back. Since turning pro at a gangly 16, he's won 22 golds in worldwide competition, broken 18 world records, many of them his own, and been named male Swimmer of the Year three of the last four years. All this, and he's just nearing his peak, which for swimmers is the early- to mid-20s. We've already seen the best out of Federer and Woods, but no one has a line on what Phelps's upside is, not even those most qualified to guess.

"In every walk of life you've got your all-time wonders, and Michael is our Einstein, our Newton," says Lenny Krayzelburg, the U.S. backstroke specialist who has won four Olympic gold medals. "What he's accomplished at 22 – complete domination – has never been done in our sport. He has a chance, before he's through, to win 25 golds at the Olympics. I laughed out loud to watch him blow away the Worlds."

"If Michael stopped today he'd go down in history as the greatest swimmer ever, but there's a number of things he can, I hope, improve on," says Bowman, Phelps's coach for more than a decade and who continues in that role while running the powerhouse men's swimming program at the University of Michigan. "His freestyle's gotten better and his breaststroke's still coming; if he continues to work as hard as he has till now, we might see drops in time still, and they could be big ones."

If there's a better – and more complex – marriage in sports than the pairing of Bowman and Phelps, it's hard to think whose it might be. The two started out with a noisy row and have been sparring and reconciling for most of 10 years, though both profess to get on better now. When Bowman came along in 1996, hired as senior coach at the North Baltimore Aquatic Club, he had a reputation as a volatile coach who didn't stay in one place very long. A former national-level swimmer at Florida State, where he earned a useful bachelor's in child psychology, he bounced from job to job during the previous decade, working at seven different places in five states.

Phelps, meanwhile, had done some bouncing himself, most of it off of the walls. From an early age he was a hyper child who jumped on the furniture, tromped his family's garden, and broke whatever was breakable in the house. "I played four sports," he says,"going from one field to another, trying to dump energy out of my system so my mom could deal with me at home." When Phelps was seven, his father Fred, a state trooper, moved out without warning or explanation. The breakup, and his subsequent rift with his father, spiked Phelps's agitation. Teachers would complain about his conduct; one of them told his mother Debbie, a school administrator, that he'd never "focus on anything in his life."

By sixth grade Phelps was taking Ritalin three times a day and being taunted by classmates for his outsize ears and a lisp that made it awkward for him to speak. Even at the pool, where he'd been sent since age seven to burn off steam after school, he was constantly being benched for bad behavior and hazed by a group of older kids. They tossed him around the water like a baby seal, stuffed him in garbage cans, piled equipment on him, and in general painted a bull's-eye on his back. One day, at a meet at Towson State, he got into it with some kids in the changing room. The place got trashed and the other boys left. Bowman walked in to find the room in shambles and gave Phelps hell for it. Phelps yelled back at him, and the two went jaw to jaw. It was the first conversation they'd ever had.

"He'd seen me at the pool, running around and being benched, and said, 'There's no way I'm training him,' " says Phelps. " 'That kid is uncoachable.' "

But Phelps, 11, was already beating kids by wide margins, and he soon moved up to Bowman's advanced group. Though fearful of Bowman, Phelps fought him nonstop, and was kicked out of practice each day for a week for failing to do a six-beat kick, a freestyle maneuver. "I had a mouth on me and my own way of doing things, and I gave Coach hell," Phelps concedes. And so it went between the tough-love coach and the fractious, gawky phenom, a loud but productive relationship that led to big cuts in Phelps's race times. That fall, Bowman sat him down with his parents and made them a stunning proposal.

"He told us that Michael was more than just fast; he was a world-class swimmer if he trained right," says Debbie. Phelps's sisters, both older, were swim stars already, and one of them, Whitney, had almost made it to the Olympics that summer, before back problems forced her to quit. "I was skeptical when Bob laid the plan out to us," says Debbie, "but Michael heard 'Olympics' and his ears stood up. Till then I never knew it was something he wanted.

What Bowman pitched the Phelpses was an all-in commitment of Michael's time and passion. "He told me I wasn't going to get where I wanted by living a normal kid life," says Phelps. "I had a tight clique of friends I grew up with from grade school, and the more involved I got with swimming, the less I got to see them. They're having parties on Friday nights and I've got a 7 am workout Saturday, so I'm staying home playing video games while my boys are out having fun." By 13, though, he'd made the cut at the Junior Nationals, shaving 10 full seconds off his time in the fly over a six-week training period. In 2000 he set records at the nationals, then went on that summer to shock everyone, Bowman included, by making his first Olympics, at 15.

But both before and after the Games, Phelps's temper flared, and he suddenly decided he was quitting to do something else. He was furious at being captive to the training grind, furious about the fun that his friends were having without him, furious at being yelled at by Bowman, who drove him ever harder as he grew. That fall they had a screaming match that lasted for hours. In the end Phelps reconsidered and agreed to go on, while Bowman, the child psych major, took a more nurturing tack with a boy who'd gone a year without seeing his father. He taught Phelps to drive and arranged for him to mentor a child with cancer, a bond that seemed to texture Phelps's view of himself and harden his resolve. He set a world record that year, won gold at the '01 Worlds at 16, and by 18 had overtaken Ian Thorpe as the dominant force in the sport. Then he swept into Athens and fell just one gold short of Spitz's mark. At 19 he found himself on top of the world, light-years ahead of the schedule Bowman had laid out to the family in 1996.

Still, Phelps, who'd come to manhood in the confines of a pool, had some growing up he needed to do. That fall he went out with his friends in Maryland and was pinched for DUI while driving home. "It was a dumb thing to do, a big mistake," he says. "I could've hurt somebody, and in a way, I did; I hurt my mom's feelings, and the people who care about me." But Phelps stepped up without prodding from handlers and instantly copped to his guilt. He apologized profusely for having done a dumb thing and went on an impromptu atonement tour, appearing in front of kids and fans to talk about drinking. It was an important step for a thoughtful teen who was just starting to figure out who he was.

At the Olympic center dining hall with Phelps, I can't help notice a group of stunning blondes at the next table. They're UCLA swimmers who have come here to train, and I'd seen them at the pool coyly circling Phelps, watching him out of the corners of their eyes. When I mention this to him, he just shrugs, oblivious. He had a girlfriend in Michigan whom he's since stopped dating and an English bulldog named Herman that he's crazy about but doesn't get to see all that much. He spends two to five hours in a pool each day, more hours eating and napping after workouts, and often hits the road for the A-list sponsors (Speedo, Visa, PowerBar, among others) that help put his annual income in the seven figures. "If I want to leave a legacy behind for my sport," he says, "this is just what I have to do."

There have been swimmers who dominated a single Games (Spitz in '72, Ian Thorpe in 2000, Phelps himself in '04), but no one has done it a second time, and the pressure on Phelps in 2008 will be severe. Apart from 2004, when he drew raves at the Games and fire for his DUI collar, Phelps has lived beyond the white-hot arc of mass-pop attention in this country, and it is fair to wonder how well he'll bear up once the full-court heat begins. It's a recipe for trouble if he pays it heed, and Phelps will be hard-pressed not to pay heed, for he is eager to represent swimming.

"I want to change my sport, push it up to the point where kids go out for swim team instead of JV hoops," he told me when we first met in Los Angeles. "I want it up at the level it's at in Australia, where guys like Ian Thorpe are giant stars and people jam in to see their meets. That's why I bust it so hard for '08. If I can do in Beijing what I did in Greece, it might just help us put it over the top."

At our last meal together he amends this slightly, saying that what he really hopes to accomplish at the Games is to bring a wave of young kids to the sport.

"Swimming's done so much for me, more than I can give back to it, and I just want them to feel some part of what I feel," Phelps says. "On my crappiest day, when I'm tired or jet-lagged, I jump in that water and just something happens that I can't even put into words. I feel better and stronger, all the soreness goes, and I'm me again, a hundred percent back."