The subcutaneous tissue (hypodermis) is the deepest layer of the skin. It is missing on parts of the body where the skin is especially thin-the eyelids, nipples, genitals, and shins. Subcutaneous tissue acts both as an insulator, conserving body heat, and as a shock absorber, protecting internal organs from injury. It also stores fat as an energy reserve in the event extra calories are needed to power the body. The blood vessels, nerves, lymph vessels, and hair follicles also cross through this layer.