It seems as if hip-hop has always been with us, at least for anyone who came of age during the past 25 years. A quarter of a century after hip-hop went mainstream with the Sugarhill Gang's release of "Rapper's Delight" - the first song in hip-hop ever to break into the Top 40 - the genre remains a hugely influential cultural phenomenon.
Songs by the latest musical heavyweights - the Wu Tang Clan, Outkast, and Eminem, to name a few - dominate radio's airwaves, soundtracks, and music awards, and continue to sell in the millions.
But what started on the streets of urban African-American neighborhoods as a fresh sound that combined bass-heavy rhythms, funk, rap, and fragments of other music, has become more than just a musical genre. Many define hip-hop as a movement, a culture, a way of life encompassing four basic elements: rap, DJ'ing, breakdancing, and graffiti art.
These forms of expression are so pervasive in popular culture today that they have become primary influences on everything from fashion to social mores.
"Hip-hop goes beyond the four standard, defining elements," says Murray Forman, professor of communications and cultural studies at Northeastern University in Boston. "As it proliferated and went through so many phases and developed in so many different ways, it escaped definition."
Such is the power of hip-hop that courses at high schools and universities across the country are incorporating hip-hop into music and literature curriculums; even museums, such as the Field Museum in Chicago, are putting together exhibitions, lectures, and conferences devoted to the subject of hip-hop and its vast influence.
Today the reach of hip-hop is global. What began as a beat-driven rumble on the street corners of the Bronx now reverberates through the white suburbs of Middle America to the high-rises of Tokyo and the favelas of Rio. Its aesthetics have influenced not only what you see on mannequins in the windows of The Gap but also the way people walk and talk. And its lyrics - sometimes politically contentious, other times materialistic and misogynistic - have become the poetry of today's youths.
Many rappers have tried to explain to their audience that the music is a part of them - Mos Def famously says, "We are hip-hop. Me. You. Everybody" - and have proudly stood on the shoulders of other musicians and poets to do so.
Even Mos Def's lyrics were borrowed from poet Carl Sandburg, who often wrote about himself as the poem, or as "the people, the mob, the crowd, mass."
This recycling of art has become a distinctive feature of hip-hop - and has come under attack over the years, particularly as MCs "cop" the lyrics of others or DJs infringe copyright law by "sampling" previous works. When DJ Dangermouse released this year's "Grey Album," in which he infused the lyrics from Jay-Z's "Black Album" with various notes and beats from the Beatles' "White Album," his work was instantly praised by music critics and decried by record labels.
But this recycling of art may actually be one of hip-hop's strengths, argues Mark Eleveld, a high school teacher in Joliet, Ill., and coauthor of "The Spoken Word Revolution: slam, hip-hop & the poetry of the next generation." "The best art forms are the ones that are pluralistic," Mr. Eleveld says. "The best forms are those that welcome all sorts of things into their voice. That's what hip-hop is all about."
Others point to beats and rhythms as the genre's strongpoint. That may account for the music's global appeal.
"My personal belief is that hip-hop begins the second your heart starts beating," says Ron Gubitz, an English teacher at Vashon High School in St. Louis and cofounder of Hip Hop Congress, a national forum of hip-hop enthusiasts. "The bass drum is the beat that really runs the whole world. And we all feel it, and we all crave it, whether we know it or not."
In many ways, the course of hip-hop mirrors that of rock 'n' roll. Invented by black musicians and put out on small, independent labels, both genres became better known as white musicians and major record companies caught on.
Since hip-hop first became mainstream, some have lamented its commercialization. "You can look at [going mainstream] as a good thing, and look at how many people it's given voice to," says Mr. Gubitz. "Or you can look at it as a bad thing and see how hip-hop as a culture left the street corners and the parties and the DJs and cardboard breakdancing and became ... a commodity."
With this notoriety came controversy - over lyrics, over image, over the influence of this genre on US culture. The cultural meaning of hip-hop remains a mystery to those whose only contact with it is through the thumping bass of passing cars.
"New social practices, especially ones that look like they're going to have a prominent influence, at some point require some explaining," Mr. Forman says. "What is this? What does it mean? Things get figured out through the arts before they become part of social consciousness."
Perhaps the popularity of hip-hop culture boils down to this: It's a vital form of expression that's available to so many with a language that has a universality to it.
"Hip-hop is pure creative expression from your soul, a medium through which people can affect and create something," says Gubitz. "That's what life is about - waking up every morning and saying, 'What is my contribution? How am I going to affect the world?' "