Your hair’s cuticle (the outermost layer of the hair shaft) is the secret to smooth, shiny hair. It is composed of overlapping, scale-like cells that form a protective layer around the inner structures of the hair. When these layers lie flat and are properly aligned, they reflect light, resulting in luster for your locks. However, when the cuticle is raised or damaged, hair can appear frizzy, dull, and more prone to breakage.