The term 'deep layer of skin' refers to the DERMA, which is the deepest layer of the epidermis. It is composed of connective tissue and is the layer of skin that contains blood vessels, nerve endings, sweat glands, and hair follicles. The DERMA also provides protection from environmental factors such as UV radiation, temperature, and bacteria. It is the layer of skin that is responsible for the production of collagen and elastin, which are important for maintaining skin elasticity and firmness.