Quick, who has the best-selling hip-hop album of all time? Eminem, Jay Z, Drake? Try Outkast. According to the RIAA, the Atlanta duo's landmark double solo release, Speakerboxxx/The Love Below, has moved 11.4 million copies, putting it above Slim Shady's The Marshall Mathers LP as the #1 rap release of all time.

The double-disc of solo albums from Big Boi (Speakerboxxx) and Andre 3000 (The Love Below) mixed the pair's signature down-South hip-hop grooves with the purest evolution of their pop smarts for a once-in-a-career phenomenon that was both unstoppable and irresistible. Andre's hit "Hey Ya" was the kind of mega-single that crossed over to every demo, as did Boi's "The Way You Move," pushing them to previously unimagined career heights.

On the 10th anniversary of the huge breakthrough -- which won three Grammys, including Album of the Year -- we spoke to Outkast and some of the people who worked on the albums to get a behind-the-scenes take on the making of the discs.

Outkast Speak

Big Boi: "We made timeless classics," Big Boi told MTV News last week at the pair's Stankonia studio in Atlanta, where the discs were recorded. "Our music don't have no expiration date on it. Same way you can pop in a Michael Jackson album, or a Prince album or an Isley Brothers album."

For his part, Big Boi integrated the group's signature skittering, uptempo hip-hop grooves with even more elements of soul and a healthy nod to the brain-frying funk of George Clinton's Parliament-Funkadelic. "It can stand the test of time. There's so many layers of music and we're saying so much, you're not going to get everything on the first listen," he said. "Ten years in, people still probably catching on to things we said in different songs and they're still jamming it ... You could set any mood to it."

Andre 3000 : "Outkast music ... it's not the easiest thing to swallow," the typically quiet half of the team told MTV News in 2003. "It's always on that fence, where people could ... hail it and love it like this is the greatest thing in the world. Or they can say, 'They have gone too far.'"

"What is too far?" a confused Big Boi wondered at the time. "There's not such a thing as too far, really, but too far away from people's ears," Andre explained. "When we're in the studio we please ourselves first ... I'm not a pop writer, but I do want everybody in the world to get a chance to listen to us."

"Friendly Competition" In Studio Sessions

Though the pair had a unified vision for what they were after, the unusual way they pursued it made their peers and label associates reasons skeptical about whether it could be pulled off.

Big Boi: "It was a concept album, completing the whole thought. Being in a group it's all about compromising," he said of the pair's decision to listen to no one but themselves. "We play a lot off of each other. But that record right there was, 'OK, this is Big's train of thought and this is Dre's train of thought.' Two sides to the same coin, but tell it in different ways."

Shannah Miller (frm. Senior Director of Video Promotion, Arista Records): "One of the first five videos I set up were 'Hey Ya' and 'The Way You Move,'" said Miller. "Listening to just the audio I knew we had something very special ... [Label boss] L.A. Reid played me the videos in his office and I was stunned. They were groundbreaking and everything you wanted a video to do ... [giving you] a reason to watch them over and over."

Killer Mike (rapper, appeared on two tracks on Big's portion): "They visited each other and listened to music, but they weren't in the same room," he said of the sessions. "That competition brings the best out of each other. That's the beautiful thing about being in a group. It's almost like being brothers ... It was beautiful to see them getting energy from one another going to each other's sessions."

Sleepy Brown: (longtime member of production team Organized Noize, sang backup vocals on Big Boi's record, the hook on "The Way You Move" and co-wrote three other Speakerboxxx songs): While Brown wasn't really privy to Andre's session, he said the double solo album concept made perfect sense to him. "I just knew Dre was gonna come up with something that was so right, I wanted to make sure as a big brother to Big that he had that record," he said. In fact, Brown didn't hear "Hey Ya" until he saw the finished video and once he did, he totally got it. "I was like, 'Oh, OK!' They was talking to each other all the time ... there was always a bit of a friendly competition," he said of the band mates.

Phillana Williams (head of marketing at Arista Records): "I went with L.A. [Reid] to Atlanta and they played the music and presented the idea to him," she said. "Being the type of creative leader L.A. was, he never once doubted their vision."

A lot of people at the label, though, were concerned: about how people would feel about not having a proper Outkast album and how radio and consumers would respond to this offbeat project. "Everyone was amazingly surprised at how well received it was," she said, noting that Boi's "Way You Move" had that signature Outkast hip-hop feel while "Hey Ya" was a departure into what she called the "Outkast of the future" sound. "When you listened to both it was almost like a historical timeline of Outkast."

"Hey" What?

Killer Mike: "I thought it was crazy. Straight up, this is insane," Mike said of the first time he heard "Hey Ya." "It reminded me of Beatles-era stuff. It was short; it was concise; it was catchy -- jingly almost. I felt like Dre finally went into singing with reckless abandon ... I remember thinking: ain't nothing going to be the same for him after that."

Big Boi: "I first heard the beat [for 'Hey Ya'] years before we put it out ... it just kind of sat around for a while," he said of the signature track from Andre's experimental half of the collection. "When I first heard it [ I said] 'This is psycho! He's a psycho!' Always surprising each other is good, because it's inspiration for each other. That's my dog, man, he ain't scared to take no chances and the feeling was there ... When I called Dre, I was like, [My son's] over here going crazy. I think you got you something!'"

Two singles? No problem

No one had ever really tried to push two competing singles from the same band to pop and hip-hop radio at the same time. But, in a series of firsts, Outkast not only ruled the charts, they did it separately, but, you know, together.

Williams: "We were doing things that had never been done," she said. "Putting out two singles from an album that was not a straight Outkast album, but one from Dre and one from Big Boi? Launching them simultaneously at radio and trying to do that at urban and pop? But then they went to all formats, because nobody wanted to be left out. Everyone wanted both songs!"

Discovering "The Way You Move"

Brown: "The beat for 'The Way You Move' was something Big had on a CD for like five years before," Brown said. "I was at his house for a cookout and he had a CD player that played like 100 CDs and that beat came on and I was sitting in the boom boom room chilling and I heard this beat. I heard that melody and I ran to Big and said, 'Yo, I got the craziest hook for this beat!' I told him to go to the studio that night and we went that night."

The rest, he said, is history. "That song flowed in just like that. You just got that feeling before you get ready to record it."

"I honestly knew it and felt in my heart Big needed that kind of record," said Brown about the importance of Big Boi having a song that could stand up to Andre's "Hey Ya." In fact, "The Way You Move" was one of the last songs Big Boi recorded for the set, and almost didn't make the cut after Brown offered to trade another beat so he could put "Way You Move" on his solo record.

Breaking All The Rules

Big Boi: "The label they was with it," he said of the album's unusual roll-out and sound. "They wasn't with the first single choices as first ... They didn't want to put out 'Hey Ya.' We was at a Vibe photo shoot and they was like, 'Nah, man we can't do that.' Me and Dre just did it strong, like, 'F--- that, we puttin' it out.' And look what happened!"

Miller: "I knew they had brought the goods, the talent and the vibe ... within a year they went from a band that had a great history at urban and hip-hop radio and couple of cooler alternative stations to being household names with Polaroid wanting to license their music."

Williams: "People expected 'The Way You Move' to do well, even though there was a concern about it being a Big Boi track without Dre. But we were all floored by how well 'Hey Ya' did," she said. Williams was on the set of the "Hey Ya" video and sensed she was watching a special moment. "At the shoot we sat there like, 'Oh my God, this is amazing.' I called L.A. [Reid] and told him, 'this if f---ing genius!'"

Killer Mike: "I like my Outkast together, so it wasn't an Outkast album [for me]," he said. "Once I got over that, I thought Big made an incredibly dense rap album and Dre made a dope hybrid album."