This chapter introduces an in vitro model as a means of studying human hormonal aging. For this purpose, human sebaceous gland cells were maintained under a hormone-substituted environment. This environment consisted of growth factors and sex steroids in concentrations corresponding to those circulating in young and postmenopausal women. The authors suggest that hormone decline, occurring with age, may play a significant role not only in the maintenance of skin homeostasis but also in the initiation of aging. Furthermore, skin, the largest organ of the body, offers an alternative approach to understanding the molecular mechanisms underlining the aging process.