(a) Generation of hemangioblasts from blastocyst-derived embryonic stem (ES) cells, or from the yolk sac or AGM region of the early embryo. Upon appropriate cytokine stimulation, hemangioblasts differentiate into angioblasts (AB) that differentiate into endothelium, which can then form capillaries. Hemangioblasts also generate HSCs, which in turn generate common lymphocyte progenitors (CLP) that differentiate into T, B, and NK cells, and common myeloid progenitors (CMP) that differentiate to erythroid, granulocyte-macrophage and megakaryocytic progenitors. (b) The pathway of generation of angioblasts and endothelial cells from the adult marrow MAPCs based on published data (16–18) showing endothelial differentiation as well as generation of MSCs and their differentiated progeny, and neural differentiation. Question marks indicate possible, not yet documented, differentiation pathways that could generate ectodermal and endodermal tissues. ±, weekly positive.