In biology, adipose tissue /ˈædɨˌpoʊs/ or body fat or just fat is loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular endothelial cells and a variety of immune cells (i.e., adipose tissue macrophages [ATMs]). Adipose tissue is derived from preadipocytes.