Final answer:
The subcutaneous tissue, also known as the hypodermis, is the fatty layer between the skin and muscles. It connects the skin to the underlying fascia of the bones and muscles, and functions as a mode of fat storage, insulation, and cushioning for the skin.
Step-by-step explanation:
The fatty layer between the skin and muscles is known as the subcutaneous tissue, also called the hypodermis. It is not strictly a part of the skin, but it connects the skin to the underlying fascia of the bones and muscles.
The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the skin.