In histology, adipose tissue or body fat or just fat is loose connective tissue composed of adipocytes. Adipose tissue is derived from lipoblasts.

Its main role is to store energy in the form of fat, although it also cushions and insulates the body. Obesity or being overweight in humans and most animals does not depend on body weight but on the amount of body fat, to be specific, adipose tissue. In humans, adipose tissue is located beneath the skin (subcutaneous fat), around internal organs (visceral fat), and in the bone marrow (yellow bone marrow). Adipose tissue is found in specific locations, which are referred to as 'adipose depots.' Adipose tissue contains several cell types, with the highest percentage of cells being adipocytes, which contain fat droplets. Other cell types include fibroblasts, macrophages, and endothelial cells. Adipose tissue contains many small blood vessels. In the integumentary system, which includes the skin, it accumulates in the deepest level, the subcutaneous layer, providing insulation from heat and cold. Around organs, it provides protective padding. However, its main function is to be a reserve of lipids, which can be burned to meet the energy needs of the body. Adipose depots in different parts of the body have different biochemical profiles.