What is the innermost layer of the skin that contains fat tissue called?

The innermost layer of the skin that contains fat tissue is referred to as the subcutaneous layer. This layer, also known as the hypodermis, acts as a cushion for the underlying muscles and bones, providing insulation and serving as a reserve for energy stored in the form of fat. It plays a vital role in thermoregulation and helps to protect the body from mechanical injury.

The dermis, while it is a significant layer of skin, lies above the subcutaneous layer. It contains connective tissue, hair follicles, and sweat glands but does not serve the primary role of fat storage.

The epidermis is the outermost layer of skin, composed primarily of epithelial cells, and provides a barrier against environmental factors. It does not contain fat tissue.

The stratum granulosum is a specific layer within the epidermis, containing granular cells that contribute to the skin's barrier function. It is not related to the storage of fat or the structure of the subcutaneous layer.

Thus, identifying the subcutaneous layer as the innermost layer with fat tissue accurately reflects its critical functions and positioning within the overall skin structure.