A hair strand consists of three layers. The cuticle is the outer layer--this layer has an average of three to ten layers that should be tightly packed together. Proper moisturizing and conditioning are important to strengthen and protect the cuticle layers. The cortex is the next layer under the cuticle--this layer determines your natural hair color and is where all permanent chemical changes (relaxers, hair dye) take place. The medulla is the inner most layer--this protein layer is hollow, and the cuticle and cortex layers shape around it. Most hair damage occurs in the cuticle layer and in extreme cases, the damage can reach the cortex and medulla. Knowing and understanding the layers of a hair strand can help you make healthier choices for your hair.