The hierarchical structure of hair in the cortex and cuticle. The main component of the cortex is a keratin coiled-coil protein phase. The proteins form intermediate filaments, which then organize into larger and larger fibres. The hair is surrounded by the cuticle, a dead cell layer. The common features observed in the X-ray data of all specimens are signals related to the coiled-coil keratin phase and the formation of intermediate filaments in the cortex, and the cell membrane complex. Signal assignment and corresponding length scales are shown in the figure.