The concept of hemangioblast was proposed a century ago. The existence of hemangioblasts has been demonstrated recently in vitro by differentiation of mouse and human embryonic stem (ES) cell into em-bryoid bodies(EBs). In the developing embryo, a common progenitor, termed "hemangioblast", generates both hematopoietic and endothelial cell lineages. The in vitro differentiation of embryonic stem cells to hemangioblast is a powerful approach for studying the commitment of the hematopoietic and endothelial lineages. This review will summarize recent development in the studies on hemangioblast.

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