The dysfunction of blood-vessel-lining endothelial cells is a major cause of mortality. Although endothelial cells, being present in all organs as a single-cell layer, are often conceived as a rather inert cell population, the vascular endothelium as a whole should be considered a highly dynamic and interactive systemically disseminated organ. This article reviewed the characteristics of endothelial cells in the entire life cycle of the vascular system, including angiogenesis, angiogenesis, maintenance of resting state, and vascular aging, providing a theoretical basis for deepening the understanding of the relationship between endothelial cells and diseases.