Abstract
Embryonic stem (ES) cells are derived from the early preimplantation blastocyst. These cells are immortal under defined conditions in vitro, and can be indefinitely expanded without loss of pluripotency. Proof-of-concept experiments demonstrate that they have the ability to spontaneously differentiate into insulin-producing cells, even if at a very low frequency. Here we review the most recent progress at defining conditions (chemical, genetic, or otherwise) for the directed differentiation of both mouse and human ES cells into insulin-producing beta cells.