Rap mogul Jay-Z thinks Nirvana temporarily halted the development of hip-hop. In rapper-songwriter-producer Pharrell Williams' upcoming book, 'Pharrell: Places and Spaces I've Been,' two of hip-hop's most successful Renaissance men discuss the cultural force known as grunge that happened to rock music 20 years ago and its effect on their own work.

"It was weird because hip-hop was becoming this force," Jay-Z told Williams. "Then grunge music stopped it for one second, ya know?"

Jay-Z believes one reason why this took place was because Nirvana and the other grunge bands were so different from what it supplanted on the charts. "'Hair bands' dominated the airwaves and rock became more about looks than about actual substance and what it stood for -- the rebellious spirit of youth," he continued. "Those 'hair bands' were too easy for us to take out; when Kurt Cobain came with that statement it was like, 'We got to wait awhile.' [Cobain] was one of those figures. I knew we had to wait for a second before we became that dominant force in music.'"

'Pharrell: Places and Spaces I've Been,' which will be released Oct. 16, features interviews with notables from the world of music, art and fashion who have inspired Williams throughout his life.