Grime has done a lot since Dizzee Rascal's Boy in Da Corner kicked in the doors of the mainstream a full 10 years ago. It rebuilt the concept of the British rapper from scratch, it has created megastars and restructured the British pop industry by allowing the children of a few square miles of London's council estates past the velvet rope and into the world of hyper-celebrity. Yet grime as music remains bizarrely indeterminate, and if you ask any five people in grime what it actually is, you will get six conflicting answers. Somehow, with labels such as Butterz, Hyperdub, Hardrive and Rinse taking its instrumentals to ever-bigger audiences, grime has avoided the ruts into which underground genres tend to settle.

But then grime has always defined itself by its refusal of definition. In 2004, Wiley made this explicit in his single Wot U Call It, mocking the record shops, punters and media confused as to where to place him among house, garage, "urban" and grime. Wiley's own genre, "Eskibeat", and terms such as "Sublow" and "8 Bar", were still being bandied about, while the instrumentals were only available in a few specialist shops.

In 2002, I had just moved to London, a jaded raver looking for a new electronic fix, and was thrilled and baffled by the deranged transmissions of pirate radio. It was clear a revolution had taken place: you could even hear it in the charts in the gulf between the rudimentary rapping and garage shuffle of So Solid and Oxide & Neutrino in 2000 and the alien electronics of More Fire's Oi in 2002. But the hundreds of tracks backing gangs of hyped-up MCs on the pirates were a mystery.

I recall awkwardly going into a record and weed paraphernalia store in Peckham and asking if they had any of those "new beats that sound a bit like electro", because this was the closest reference point I could find for the spiky rhythms and electronic funk. The assistants – old garage heads who clearly loathed this racket the kids were making – dismissively lobbed a pile of white labels on to the counter.

For others, hearing these beats was the beginning of a DIY explosion. Spooky Bizzle, DJ and producer of Slew Dem crew, says: "If it wasn't for the tunes that built the foundation, like Danny Weed's Creeper, Dizzee Rascal's Hoe, Wiley's Eskimo or Youngstar's Pulse X" – the record considered the first-ever grime release, from early 2002 – "or even watching my peers around me constructing their own grime beats, then I wouldn't be doing what I do now."

West Londoner Shy One describes the thrill of hearing "the energy, the grittiness, the rawness" on radio: "It was like the sound of London, of my generation, of us," she says. "I wanted to make the beats when listening to and mixing them weren't enough."

Maverick south Londoner Darq E Freaker cites mischief-maker Jammer as very influential: "I was making garage-type beats before that, but he came with a hip-hop influence, that east-London sound; that was really new." That newness was the result of a true youth explosion. "It was young music; it wasn't like garage or jungle where older guys ran it," explains scene originator Footsie, of the Newham Generals. "This was young people with no rules." Mancunian DJ Chimpo agrees: "With no production education or training, they had to experiment, which led to the most interesting dance music around and made it acceptable to do some strange things within the genre."

The story of how grime got from that initial explosion of chaotic, untutored brilliance and insular self-reliance to the point today where an outsider such as me could put together a compilation of beats from as far afield as Ireland and Japan, without losing that sonic strangeness, could fill books. (With the exception of certain countries – the Netherlands and, more unexpectedly, the Czech Republic – there are no real grime "scenes" internationally, but thanks to bloody-minded obsessives such as Juzlo in Australia, Prettybwoy in Japan, Major Grave in Ireland or Starkey and Team Shadatek in the US, grime is a global affair.)

It's a coming-of-age tale involving friendships, rivalry, violence, police persecution, the absorption of the scene's biggest names into the showbiz world, getting eclipsed by the sound's suburban first cousin, dubstep, and subtle but powerful changes to British cultural identity.

Darq E Freaker: 'This was really new. This was young people with no rules.' PR

What is sure, as Shy One says, is that "it hasn't become a trend or a fad at any point – individual artists might change their sound if they're picked up by labels, but grime itself is influenced by nothing". Experimental grime and house producer Visionist is concerned there could be a commercial orthodoxy – "people at the forefront don't bring that much new – they're good tunes, but a kind of rebirth of what Rude Kid and Maniac did in 07-08" – but the very fact that his own Lost Codes label can push some of the eeriest, most out-there grime instrumentals to an increasingly wide audience shows that it's still the broadest of churches.

It's not all rosy. The gulf between grime and the rest of the music industry, though bridged by a few, remains. "Ask people to name people in grime," says Darq E Freaker, "and they might know Dizzee and two or three others, and those are the only ones making money out of it." But for all that it is the awkward and prickly child of UK rave, the tenacity, love and enthusiasm within the grime scene is something to behold. That same self-reliance and weirdness that came of being teenage rejects may just prove to be grime's saving grace as it grows up.