Skin aging appears to be the result of both scheduled and continuous "wear and tear" processes that damage cellular DNA and proteins. Two types of aging, chronological skin aging and photoaging, have distinct clinical and histological features. Chronological skin aging is a universal and inevitable process characterized primarily by physiologic alterations in skin function. In this case, keratinocytes are unable to properly terminally differentiate to form a functional stratum corneum, and the rate of formation of neutral lipids that contribute to the barrier function slows, causing dry, pale skin with fine wrinkles. In contrast, photoaging results from the UVR of sunlight and the damage thus becomes apparent in sun-exposed skin. Characteristics of this aging type are dry and sallow skin displaying fine wrinkles as well as deep furrows, resulting from the disorganization of epidermal and dermal components associated with elastosis and heliodermatitis. Understanding of the functions of the skin and the basic principles of moisturizer use and application is important for the prevention of skin aging. Successful treatment of dry skin with appropriate skin care products gives the impression of eternal youth.