Against all odds, Williams sisters have dominated tennis for years

Who would have thought these siblings from Compton, Calif., would combine to win 16 Grand Slam titles? Paul Harris/Online USA

Key moments of the Open era: Part 4: Crossing the millenium (1998-2007)

1. Two at the top
The success of Venus and Serena Williams is one of the greatest stories in the history of sports. At least the Manning brothers grew up the children of a quarterback and in an affluent part of New Orleans. Venus and Serena were raised in Compton, Calif., quite a distance from lily-white tennis clubs. Their father Richard had proclaimed they would in time rule the sport. And for just under two years, they did. From the 2001 U.S. Open to the 2003 Wimbledon, the two met in six of seven Grand Slam finals. Even beyond that, though, Venus and Serena have won a combined 16 Grand Slam singles titles. Just imagine Tiger Woods' brother chasing him down at Augusta and you'll see just how amazing this story is.

2. Royal Roger
No sooner had the Pete Sampras era ended when another man emerged on the scene -- one who could well end up being the greatest player in tennis history. Roger Federer had worked long and hard to fulfill his potential, laboring for half a decade on the tour to make his way up the ranks. Once he arrived at the top, he became a remarkable force, his tranquil manner and, most of all, his captivating artistry and skill leaving fans and even long-standing legends swooning.

3. Going out on top
Coming into the 2002 U.S. Open, it had been more than two years since 31-year-old Pete Sampras had won a singles title. Earlier that summer, at Wimbledon, he'd gone out in the second round. But in New York, Sampras once again found his groove. Reunited with his longstanding coach, Paul Annacone, Sampras followed a simple guideline: Use your athleticism. Showcasing the clinical precision and attacking style that made him the world's best, Sampras made his way to the finals where he encountered a familiar rival: Andre Agassi. Once again, he rose to the occasion, serving brilliantly, moving forward, closing it out with a knife-like backhand volley to become only the second man in tennis history to win Grand Slam singles titles in his teens, 20s and 30s. Months later came the announcement: Sampras was retiring. It had been a storybook close to an epic career.

4. Rising Rafa
He's only 22, so it's likely there'll be more chapters coming in the Rafael Nadal story. But already he's made a distinctive mark on tennis history. Picking up the mantle from such lefty ancestors as Guillermo Vilas and Thomas Muster, Nadal first emerged as the grinder par excellence, a hunk of fiery passion virtually unbeatable on clay. At the 2005 French Open, Nadal became the first man in more than 20 years to win a Grand Slam event the first time he ever played -- and as the world now knows, has since earned his fourth consecutive title there. But rapidly Nadal has proved himself no one-surface pony. His fellow Spaniards have often been intimidated away from clay. Not Nadal. Early in his career he won several hard-court titles. Then, this summer, he again etched his name into tennis history when he became the first man since Bjorn Borg 28 years ago to win the French Open and Wimbledon in the same year. And yet, mere achievements are only part of what makes Nadal compelling. His swashbuckling manner, distinctive wardrobe, first-rate sportsmanship and obsessive rituals -- who else could get away with biting his trophies? -- have earned him a commanding following.

5. Russian revolution
Tennis' return to the Olympics in the early '80s dramatically raised its profile all over the world -- nowhere more than in the medal-happy USSR. Many Russian ex-Olympians recognized getting their children into tennis could be both prestigious and lucrative. By the late '90s, the USSR had been dissolved -- but the tennis revolution was unabated. Ambitious players such as Anna Kournikova and Yevgeny Kafelnikov burst on to the scene, winning matches and earning money. Other Grand Slam champions followed in flood-like proportions, from Marat Safin to Anastasia Myskina, Maria Sharapova and Svetlana Kuznetsova -- and a host of other contenders who continue to make a major mark week in and week out.

6. Agassi's image turns into substance
It was May 1999, and Andre Agassi had just turned 29. At this point in his career, his fame seemed more prominent than his game: It had been more than four years since he'd last won a Grand Slam title. That month a shoulder injury made him ponder not even entering the French Open. But Agassi's coach, Brad Gilbert, convinced him it was worth giving Roland Garros a go. Rallying from behind in several matches -- including a two-sets-to-love deficit in the final -- Agassi earned his sweetest title, becoming only the fifth man in tennis history to have earned singles crowns at all four majors. The victory spurred him to go on and reach the Wimbledon final, win the U.S. Open, and for the only time in his career, finish the year ranked No. 1 in the world. He'd subsequently win another three Australian Open titles. Considered a waste of talent early in his career, once Agassi retired in 2006, it was clear once and for all that he'd left nothing on the table.

7. Equipment makes a major mark
The 21st century has seen dramatic shifts in how professional tennis players approach equipment. For decades, this was the paradigm: world-class players used heavier rackets, lively strings and big grips so the frame would not twist. But in recent years, much has changed. The introduction of Luxilon, a dead string, has made it possible for pros to strike the ball with exceptional racket-head speed, generating unprecedented levels of speed and spin -- and dramatically making tennis even more of a hard-hitting, baseline-driven game. To aid their quest for significant torque, players such as Nadal are using far smaller grips. Grass, hard and indoor courts have also slowed down considerably, increasing the length of rallies and placing a premium on physical fitness. At this point, net-rushing is far less visible than it has been in more than 50 years. But the history of any sport is a tale of cycles. Competition drives improvements -- and to conquer one prevailing style, new playing styles emerge.

8. Small nations, big players
Perhaps the truly great champions come more from the skies than from the ground. Greatness might well have more to do with personal desire than any form of institutionalized effort. To prove this point, look no further than the players who emerged from such tiny nations as Belgium and Serbia -- eager, skilled, engaging. Justine Henin and Kim Clijsters turned Belgium into a significant force on the tennis scene. Currently the same is occurring with Serbia, evidenced by the ascent of Ana Ivanovic, Jelena Jankovic and Novak Djokovic.

9. The new adventures of the old Martina
She'd retired from singles competition after 1994, but in 2000, 43-year-old Martina Navratilova decided it was worth returning to play doubles. For seven years, she competed well, winning titles, retooling her game, her presence rapidly becoming less a novelty and more business as usual. In 2003, she and Leander Paes won the mixed doubles title at Wimbledon, her 20th title there -- tying Billie Jean King's record. Three years later, a month shy of turning 50, she closed out her career magnificently, winning the U.S. Open mixed doubles title with Bob Bryan.

10. Here comes China
On the other hand, perhaps a top-down effort can indeed generate new champions. As China's market economy grows, its people seek status -- and few sports are better at conferring social prominence to aspiring societies than tennis. So it goes that tennis is on the rise in the world's most-populated nation, a potential boom of epic proportions that could dramatically alter everything from the sport's geographic and economic centers of power to new ideas about coaching and player development.

Joel Drucker is based in Oakland, Calif., and writes for Tennis Magazine and Tennis Channel.