Yasiin Bey, better known by his stage name Mos Def, is an American rapper, singer, actor, and activist. Best known for his music, Bey began his hip hop career in 1994, alongside his siblings in the short-lived rap group Urban Thermo Dynamics, after which he appeared on albums by Da Bush Babees and De La Soul. He subsequently formed the duo Black Star, alongside fellow Brooklyn-based rapper Talib Kweli, and they released their eponymous debut album in 1998. He was featured on the roster of Rawkus Records and in 1999 released his solo debut, Black on Both Sides. His debut was followed by The New Danger, True Magic and The Ecstatic. The editors at About.com listed him as the 14th greatest emcee of all time on their "50 greatest MC's of our time" list. Some of Mos Def's top hits include "Oh No", "Definition" and "Respiration".