The deepest layer of the skin, made of fatty tissue that insulates and cushions the body, is the:

The subcutaneous layer, also called the hypodermis, is the deepest layer of the skin. It is composed largely of fatty (adipose) tissue that insulates the body, stores energy, and cushions underlying structures. Above it lie the dermis (the living layer with vessels, nerves, and glands) and the epidermis (the outer protective layer). Recognizing the subcutaneous layer's composition and role — and its position as the deepest skin layer — is part of the foundational skin anatomy assessed on the exam.