Endothelial stem cells are one of three types of stem cells found in bone marrow. They are multipotent, which describes the ability to give rise to many cell types, whereas a pluripotent stem cell can give rise to all types. ESCs have the characteristic properties of a stem cell: self-renewal and differentiation. Since clear definitions exist for identifying cells with stem and progenitor cell properties in many tissues and organs of the body, several groups have begun to accumulate evidence that endothelial stem and progenitor cells exist within the endothelial intima of existing blood vessels. These include numerous processes, such as blood vessel formation, coagulation and fibrinolysis, regulation of vascular tone, to a role in inflammation. Endothelial cells originate from the mesoderm, a germinal layer that forms at gastrulation, an early embryonic development stage.