Recent discoveries of molecular markers for arterial, venous, and lymphatic endothelial cells (ECs) made it possible to investigate mechanisms of the vascular diversification at the cellular level. Recently, these three EC types have been successfully induced from mouse embryonic stem cells. Molecular and cellular dissection of EC diversification processes in vitro using embryonic stem cell system would provide novel insights into vascular development and materials for cell therapy as well as gene therapy and novel drugs. Further investigation of tissue-specific vascular diversification in detail would be important for future vascular biology and medicine. (c) 2007, Elsevier Inc.