Seven years after his blockbuster solo debut The Chronic permanently altered the state of hip-hop, Dr. Dre still had a chip on his shoulder. The former N.W.A. kingpin channeled that determination into the long-gestating follow-up 2001, which brought back previous collaborators like Snoop Dogg alongside his latest protégé, Eminem. To mark the 20th anniversary of its release, Dre and music mogul Jimmy Iovine reminisce about the album’s creation and its legacy.