Mos Def is a Brooklyn-born rapper and actor, who actually began his performing career on The Cosby Mysteries in 1994. He switched to rap music and worked with De La Soul and da Bush Babees before releasing his own first single, "Universal Magnetic". It did quite well, and he moved to Rawkus Records. Mos Def and Talib Kweli released Black Star, a full length album, in 1998, with DJ Hi-Tek as producer. Mos Def released his solo debut, Black on Both Sides, in 1999. After the collapse of Rawkus, Mos along with Talib signed on to Interscope/Geffen.
An earlier generation of rappers, including Brand Nubian and De La Soul, had made some groundbreaking, thoughtful rap music. They had been replaced by gangsta rap though, and Mos Def was one of the principal causes of a revival in such socially aware rap, which also involved Dr. Octagon, Kweli, Common and others.
He returned to acting in 2000 and has starred in Monster's Ball , Bamboozled, and the 2003 remake of the The Italian Job. He also starred in Topdog/Underdog on Broadway, and in 2004 he starred in the HBO movie Something the Lord Made. Currently he stars in the Hitchhiker's Guide to the Galaxy movie as Ford Prefect and hosts the award-winning show Def Poetry on HBO.
He was also part of Black Jack Johnson, an all-black rock group (also including Dr. Know, Bernie Worrell, Doug Wimbish and Will Calhoun) to rescue rock music from what they saw as boring and staid groups, such as Limp Bizkit, whom Mos Def openly despises. The group has performed a few concerts.