Abstract: A method of propagating embryonic stem (ES) cells in an undifferentiated state, while maintaining both the pluripotency and the cells normal genotype is disclosed. The method comprises using recombinantly produced protein domains to attach human embryonic stem cells to the surface of a bioreactor. The ES cells are supplied with nutrients while they held in place by the recombinantly produced protein domains which may be chosen from Laminin G domain, Fibronectin domain 2, Fibronectin domain 3, Nidogen G2 domain, Nidogen G3 domain, Vitronectin somatomedin B domain, and Vitronectin somatomedin C terminal domain. Useful molecules are characterized by a high binding affinity for hES cells and a molecular weight of about 50 kDa±20%.