What is the part of the hair that contains pigment?

The cortex is the part of the hair that contains the pigment responsible for the color of the hair. It is the thickest layer of the hair, situated between the outer cuticle and the inner medulla. The cortex is made up of long, coiled keratin fibers, and it is within this layer that melanocytes, the cells that produce melanin, are located. Melanin is the pigment that gives hair its color, and different types and amounts of melanin result in variations in hair color.

While the cuticle is the outer layer that protects the hair shaft, and the medulla is the innermost layer which may or may not be present in all hair types, neither of these layers contains pigment. The hair shaft is the visible part of the hair that extends beyond the scalp, but it is the cortex that is responsible for the pigmentation. Therefore, identifying the cortex as the area containing the pigment accurately reflects the biological composition of hair.