Prominin-1 (CD133) is a pentaspan membrane glycoprotein that binds to plasma membrane cholesterol and concentrates selectively in plasma membrane protrusions. In recent years, this molecule has received considerable interest due to its expression in various progenitors, including those derived from the neural and hematopoietic system, as well as in cancer originating from these systems. Prominin-1 is also the target of mutations leading to retinal degeneration. In the future, prominin-1-positive progenitor cells might become clinically significant, particularly with regard to tissue engineering, and prominin-1 itself might reveal some fundamental cell biological aspects concerning the self-renewal capacity of somatic stem cells