The fatty layer of skin that stores energy is called the subcutaneous fat, also known as hypodermis.

Here's why:

* Location: It sits beneath the dermis (the middle layer of skin) and above the muscles and bones.

* Composition: It's primarily made up of adipocytes (fat cells) which store triglycerides, a type of fat that is a highly efficient energy source.

* Function: Besides storing energy, subcutaneous fat also provides insulation, cushioning, and helps regulate body temperature.

Let me know if you have any other questions!