Eminem first dissed the "Genie In a Bottle" singer in 2000 on his song "The Real Slim Shady."
Eminem came up through Detroit's underground rap battle scene, where MC's who spit the funniest, wildest rhymes reigned victorious. After his debut album Infinite flopped, he concocted the 'crazy' Slim Shady persona, who evokes the 'anything goes' battle rap mentality.
Ironically, that tactic turned Marshall Mathers into one of the biggest musical artists in the world. Today he still crafts cheeky bars about pop stars, but he's just as likely to collaborate with them.