White adipose tissue primarily stores energy in the form of long-chain fatty acids and triglycerides. However, the tissue, which is usually directly below the skin, also acts as a cushion that protects against bodily impact and as insulation to keep the body warm. Depending upon the species and age of an organism, brown adipose, which derives its coloration from densely packed mitochondria, may be found in a variety of locations in the body. The tissue is more metabolically active in hibernating animals and can be activated by cold weather.