BioTime, a California biotech company headed by Michael West, a prominent scientist and entrepreneur involved in stem cell research, plans to supply scientists working with stem cells the tool they most need to develop and test novel therapies–a reliable and reproducible source of the cells.

They plan to sell human embryonic progenitors, cells that have inched partway along the continuum from embryonic stem cell to differentiated adult cell and can reliably generate cells that reproduce only the same type of cells.