Almost the only thing certain about dubstep is that it's all about the bass. In fact, the genre is sometimes simply called "bass music" -- increasingly so, in fact, the further it strays from its dubwise origins in U.K. soundsystem culture and mutates in a dozen directions at once. Dubstep began, around the turn of the millennium, as a dank, skulking riposte to the effervescence of U.K. garage, with a half-time skank encased in stony reverb. From the dark garage of Horsepower Productions and El-B sprang a heavier, more brooding sound at the hands of Skream, Benga, Digital Mystikz, and their peers in the London and Bristol undergrounds. Such labels as Kode9's Hyperdub (home to Burial) and Mike Paradinas' Planet Mu helped push the limits of the sound throughout the late '90s, while Caspa and Rusko gave the music a cheeky sense of swagger. It was the latter pair who first truly caught the fancy of American ears, which have increasingly turned to the hard-edged wobble of the "brostep" contingent. By 2011, even Britney was jacking dubstep cadences, Magnetic Man (a super-group of Benga, Skream and Artwork) crossed over to the pop charts, and former emo kid Skrillex emerged as the genre's first poster boy.