A type of connective tissue that is specialized for the storage of neutral fats (lipids). Adipose cells originate mainly from fibroblasts. In the mammalian embryo, development of adipose cells starts at an early stage. The two types of adipose cells have names reflecting their gross physical appearance: white fat, which can be yellowish if the animal's diet is rich in carotenoids (as found in tomatoes), and brown fat, containing vascularization and respiratory pigments.