There are 3 distinct layers to the structure of the skin. These layers can be defined as
1. Epidermis or outer layer which in itself contains 5 sub layers
2. Dermis: composed of 3 types of tissue namely collagen, elastic tissue and reticular fibers
3. Hypodermis or Subcutaneous tissue: a layer of fat and connective tissue that houses larger blood vessels and nerves
Depending on the clinical endpoint you are hoping to achieve the lasers may be working on one or multiple layers of the skin. A basic understanding of these layers will help you to understand the level of improvement that can be achieved.