Medulla -- Hair Cortex and Hair Cuticle -- Inner Root Sheath -- Outer Root Sheath and Companion Layer -- Hair Bulb and Papilla.Each and every hair is much more than just the visible shaft—there are also associated complex sheath structures of epidermal and dermal origin. In the hair follicle, cells undergo a variety of differentiation processes, mostly depending on their layers and positions therein, and electron microscopy reveals a very complex architecture. The structure of a particular layer, such as Henle’s layer of the inner root sheath, is not uniform. Rather, cells drastically change during the course of differentiation. By simply comparing electron micrographs of cells of a layer at different degrees of differentiation, one can hardly recognize them as belonging to the same layer. As readers will see, this book contains many superb electron mic- graphs, from low-magni?cation panoramic views for orientation to hi- power views showing ultrastructural detail. Captions and schematic drawings are also very helpful in “reading” electron micrographs and - derstanding the structural detail. In this way, Dr. Morioka has succeeded in dissecting the complex hair follicle at the ultrastructural level.