Ariel LeBeau for Fuse

The ideal place to catch U.K. electronic duo Disclosure would probably be during a midnight show at an under-the-radar London club. But we somehow managed just fine with our second-best option: their 6pm set at the Grove Stage Friday evening in front of the iconic Chicago skyline at Lollapalooza 2013.

Despite sharing a set time with It indie band Imagine Dragons and icons like New Order and Queens of the Stone Age, the brother duo (Guy and Howard Lawrence) still managed to fill their small section of Grant Park to the rim. It was muggy and humid after showers drenched the grounds earlier in the day, but fans spilled out all the way onto Columbus Drive to catch a glimpse/dance their asses off.

The giant crowd came as a bit of a shock. "I really thought we'd be one of, like, 300 people over here," one British fan said as he made his way to the stage. But judging by Disclosure's YouTube numbers alone—they're biggest hit, "Latch," has over 18 million views—we shouldn't be that surprised. Their Internet popularity has translated to album sales, too. Disclosure's debut album Settle sold over 40,000 copies and rocketed them to the top spot on both the U.K. Albums Chart and the U.K. Dance Albums Chart. Not too shabby for a couple of young kids from Surrey.

The crowd fist pumped along to every song with equal intensity. After knocking their opening track "F for You" out of the park, they continued the party with Settle faves "When A Fire Starts To Burn, "You & Me" and "Latch." But the short short-sporting crowd really let it all hang out during "White Noise," their AlunaGeorge-assisted banger. So. Much. Twerking. And in case you were wondering, yes, crowdsurfing is appropriate at a Disclosure show.

"We love Chicago and everything that its music has done for us," Howard told the crowd. He's referring, of course, to Chicago's historied house music scene. Artists like Vince Lawrence and Felix da Housecat along with record label Trax Records helped make Chicago house a bonafide movement in the early '80s. Is now when I tell you Guy and Howard weren't even born until the '90s?

Yeah, that means Guy and Howard are 22 and 19-years-old (respectively), making them the same age as most of their fans. And at a festival where two of the four headliners could be considered throwbacks likely booked to get Gen X-ers back into the fest (The Cure and Nine Inch Nails), it's safe to say the kids want their electronic music. Well, the kids, and one seriously kick-ass Grandma in a floral dress who took pictures during the entire set. The Disclosure fire is starting to spread.

Check out all the best photos from day 1 of Lollapalooza: