Eminem's world has never been as sprawling as that of, say, Rick Ross. Throughout his career, Em has nurtured a tight circle of Detroit emcees, whether it's his crew D12, his longtime friend Royce Da 5'9" of Bad Meets Evil, or locals like Trick Trick and Obie Trice. His first major guest appearance was on Kid Rock's Devil Without a Cause, before the two had a falling out. In 1999, the year Em dropped his Slim Shady LP breakthrough, he appeared on several projects issued by then-hot New York backpack empire Rawkus, including the High & Mighty and DJ Spinna, and briefly associated himself with New Jersey group the Outsidaz.
Since then, the bulk of Eminem's freelance work has been via Dr. Dre's Aftermath camp, from Xzibit to 50 Cent's G Unit. He has had mixed success with his Shady Records empire; many of the names on his 2006 comp The Re-Up, like Stat Quo and Bobby Creekwater, subsequently disappeared, but Yelawolf and Slaughterhouse's major-label albums made it to stores. In recent years, Em has mentored pop singer-songwriter Skylar Grey. He occasionally builds with fellow megastars like Jay-Z, Lil Wayne and T.I. It's a rare and pleasant surprise when Eminem drops a verse for someone that doesn't fit these categories, like when he jumped on B.o.B's "Airplanes, Part II." The Detroit icon is the most deliberate of cameo kings; he doesn't make false moves.