Rapper Eminem is 'scared' by the massive commercial and critical success that has made him a global superstar, according to his biographer.
An icon to millions - or the 'biggest threat since polio'?
The star has encountered ever-growing adulation on the back of the film 8 Mile, loosely based on his youth in Detroit, and his album The Eminem Show.
Eminem's friend and biographer Anthony Bozza has argued that they revealed a different side to Eminem - and he has been increasingly accepted by the establishment as a result.
"In 2003, he really jumped a whole level," Bozza told BBC World Service's The Ticket programme.
Through his film and latest album, "more people were able to access what he's really talking about - his hard life, his dysfunctional family, being the child of a single parent," he said.
"More people were able to get into Eminem. People like Barbara Streisand, politicians - more than ever before.
"Frankly he's pretty scared by it."
Leading poet Seamus Heaney earlier this year praised Eminem for his "subversive attitude" and "verbal energy."
And 8 Mile brought the rapper an Oscar for Best Song - Lose Yourself - in March.
Barbara Streisand is a confirmed Eminem fan
Bozza said people were beginning to understand the experiences behind some of Eminem's songs - mainly thanks to the success of 8 Mile.
"It was incredibly accurate in the look and feel of what it really is like in the part of Detroit where Eminem grew up and where he spent his time," Bozza said.
The biographer, who grew up with Eminem in Detroit, said the authenticity of 8 Mile came in part from Eminem himself.
"He had a lot to do with going over set design, down to the stickers that his friends have their wall in the basement where they hang out.
"His story has been changed a bit - things were definitely altered from the life story - but I think you really get a sense of the feeling of where he's from and how he grew up."
Bozza said Eminem - once described by US President George W Bush as "the most dangerous threat to American children since polio" - was now reacting to the cult of celebrity that had grown up around him.
Songs like Superman and Business - which criticise the music industry and celebrity status - were his way of venting his frustrations.
"I think he's got a lot of other things to be frustrated and angry about, which really does feed his music," Bozza stated.
"He's very passionate, reacting to things in his life."
Bozza, who recently completed his study of his friend, Whatever You Say I Am, conducted Eminem's first mainstream interview.
"I knew he was different - he was using different vocabulary, he had a different style - but I still didn't know how people would take him," Bozza said.
"I didn't know how long he could sustain it, and what I really couldn't predict is how much his rap style has evolved and progressed and gotten better.
"At the same time, hip-hop also has grown into this tremendous international language, so Eminem is the top rapper everywhere, from Taiwan to South America - it's not just Europe and the US anymore."