Previous research has confirmed that hematopoietic cells and endothelial cells originate in a common mesodermal precursor named as hemangioblast at specific time and locations during embryonic development. Hematopoietic cells and endothelial cells were originated gradually from hemangioblast by specialization, determination and differentiation step by step. The author reviews the origin, markers, commitment, and differentiation of hemangioblast, and presents some research evidence on the transcriptional factors and influencing genes for the specialization of hemangioblast. Further research on specialization genes of the hemangioblast will be critical for a better understanding of the events involved in hematopoietic and endothelial cell differentiation as well as for utilizing this cell population for clinical applications.