The development of many different cell types such as muscle, blood, and skin is known as cell differentiation. ‘Cell differentiation and stem cells’ shows how this first occurs in the developing embryo and continues after birth and throughout adulthood. The character of specialized cells is the result of a particular pattern of gene activity that determines which proteins are synthesized. Gene expression is under a complex set of controls that include the actions of transcription factors, and chemical modification of DNA. The importance of stems cells, including their potential in regenerative medicine, hematopoiesis (blood formation), and apoptosis (cell death) are also discussed.