Endothelial cells line the interior of all blood vessels, composing the endothelium. All endothelial cells are derived from a common angioblast precursor and subsequently develop organ specific properties. Embryonic endothelial cells exhibit much heterogeneity within, and between, organs. Differentiation of endothelial cells is governed by several factors, including the immediate microenvironment, interactions with surrounding cells, and the local release of cytokines and growth factors. Adult endothelial cells retain remarkable plasticity and are known to reprogram in response to IL-1, TNF, VEGF, and FGF. Because endothelial cells provide many essential functions, endothelial dysfunction leads to vascular disease and can promote the development of chronic inflammatory conditions, such as atherosclerosis. R&D Systems offers a range of quality products for the identification and characterization of specific endothelial cell types.