What layer of the hair contains the cells that hold melanin responsible for hair color?

The cortex is the layer of the hair that contains the cells responsible for holding melanin, which determines hair color. The cortex is situated between the outer cuticle and the innermost medulla and consists of long, fibrous proteins that provide strength and structure to the hair shaft. Within the cortex are specialized cells that produce and store melanin, the pigment responsible for various hair colors, from black and brown to blonde and red. The amount and type of melanin in the cortex influence the specific shade of a person's hair.

Other layers and structures, such as the medulla and cuticle, do not contain melanin. The medulla, which may be absent in some hair types, is the innermost layer and typically does not participate in coloration. The cuticle is the outermost layer and serves primarily as a protective barrier for the hair but does not play a role in determining hair color. The follicle, which is the structure from which hair grows, contains the hair root but again does not hold melanin itself. Understanding the role of the cortex in hair coloration is crucial for anyone studying hair biology or working in electrolysis and laser treatments.