The skin is the largest organ of the body and consists of more than just the epidermis. It has three layers - the epidermis, dermis, and subcutaneous layer. The epidermis is the outermost layer made of keratin. Below this is the dermis containing collagen fibers, glands, nerves and blood vessels. The deepest layer is the subcutaneous layer made of fat cells that insulate and protect the body. The skin along with hair, nails and glands make up the integumentary system.