Ah, the '90s. Feeling sentimental yet?

Those good old days are less than five years old, but already we're awash in '90s nostalgia.

In July, VH1 debuted its "I Love the '90s" series, which reflects on the pop culture of the decade. This fall, a '90s-themed nightclub named Nirvana will open in New York, and Nick at Nite will begin airing reruns of "The Fresh Prince of Bel-Air." And Trivial Pursuit recently launched a '90s Time Capsule Edition board game.

The game's marketing campaign began with a traveling time capsule that stopped in eight cities. Kato Kaelin, houseguest of O.J. Simpson and accidental celebrity of 1995, donated a house key to the capsule. Cute.

But last time we checked, the '90s ended, like, five minutes ago. How can we possibly be nostalgic?

Chuck Underwood can explain it simply.

"Nostalgia is simply a proven, effective marketing and advertising tool," says Underwood, a generational consultant in Cincinnati. "Most Americans have fond memories of their formative years, and marketers have been able to capture that nostalgia."

Unlike '70s and '80s flashbacks, which have permeated everything from furniture to fashion, '90s nostalgia is in its infancy. It is being targeted exclusively to the prized 18- to 34-year-old demographic—consumers who are still learning about the harsh realities of the real world and want to cling to something familiar.

"We're starting to learn that anything that's 10 years old is considered retro," says Tim Ouellette, co-founder of '70s club Polly Esther's and '80s-themed Culture Club in New York and the soon-to-open Nirvana.

Originally, VH1 producers worried that it was too soon to reflect on the '90s. But they researched and laughed at phenomena such as Twin Peaks, Jason Priestley's sideburns and other "I can't believe we liked that" slices of pop culture. Besides, fans were requesting an "I Love the '90s" program.

"We take a comedic approach to things, looking back and celebrating but also trying to mock a passage of time," says Meredith Ross, VH1 executive producer.

THE 9/11 FACTOR

Other cultural observers point to something more poignant at work: nostalgia for life before 9/11, a time before orange alerts and weapons of mass destruction nagged at our sensibilities.

"The world has changed so much in four years," says Cara Lynn Shultz, entertainment editor for Stuff Magazine. "Then, our biggest concern was, 'Will our computers shut down for the millennium?' America was this great invincible machine. ... The '90s really were the good old days."

Kevin Howley, a professor of communications at DePauw University in Indiana, calls the '90s a "virtual decade," a period tinged with unreality: We enjoyed a virtual economic boom and virtual communication made possible by the Internet.

Even the news seemed unreal: The Bill Clinton-Monica Lewinsky scandal dominated the national discourse, and the villains were Lorena Bobbitt and Tonya Harding. We finished off the decade with boy bands and bubble-gum pop.

"It was a time of candy-coated America, and the music reflected that," Shultz says. Though in retrospect the '90s might seem idyllic, it was not a golden era, Howley says. "Nostalgia is shorthand. We're longing to find the good stuff, and when we look backwards we often don't think about the more pressing problems."

But for some, the problems of the '90s don't compare to the problems of this decade.

Anthony Pomes compares the transition from the '90s to the segue from the Roaring '20s to the Great Depression.

"The ('90s) images are anesthetizing us," says Pomes, who was the chief research editor for the pop-culture book "Joe Franklin's Great Entertainment Trivia Game." "We want to clutch on to something, to anything, to fill the gaping hole that was left by the attacks on the towers."

WHAT WERE THE '90S?

Of course, not everyone reflects on the '90s through the lens of Sept. 11.

At the University of Central Florida, members of the campus Jewish group Hillel are planning a '90s-themed Shabbat. The evening will include slap bracelets.

"It's the first decade that I can really remember," says Amy Schwartz, 20, Hillel secretary.

Schwartz hopes the theme will draw students to the event and give them a conversation piece.

That's exactly what '90s nostalgia gave Dana Karen when she moved into her dorm at UCF. Karen, 19, has bonded with floormates by watching reruns of "Dawson's Creek" and "Saved by the Bell."

Still, other than tracing Tiffani-Amber Thiessen's career, it could be too early to reflect on the important events of the '90s

And there are some things we might never be able to explain.

Remember Kris Kross, the rap duo who wore their clothes backwards? Why was the macarena so popular? And what does Vanilla Ice's "Word to Your Mother" mean?

We love to pigeonhole a decade into a few pithy images: The '70s are disco and girls with long hair; the '80s, yuppies and girls with big hair.

But the '90s, which covered everything from grunge to gangsta rap, are harder to classify.

Jerry Maguire heard, "Show me the money!"

Forrest Gump mused, "Life is like a box of chocolates."

The '90s are somewhere in-between.

Now the question is, when will we get nostalgic for this decade?