The function of the human nail is to assist in picking up small objects, to protect the distal digit, to improve fine-touch sensation and to enhance the esthetic appearance of the hands. A complete understanding of the anatomy and physiology of the nail is essential todecipher its mysteries and its response to pathological processes. The nail is a unique structure whose component parts are collectively called the nail unit. The nail unit consists of the nail matrix, the nail bed, the hyponychium and the proximal and lateral nail folds. Anatomic structures of the nail include, from distal to proximal, the hyponychium, the onychodermal band, the nail bed, the nail plate, the lateral nail folds, the lunula, the cuticle, the nail matrix, and the proximal nail fold.