Dermatopathology deals with the microscopic study of skin, adjacent mucosa, and cutaneous adnexal structures. Dermatology and dermatopathology put much emphasis on clinical and pathological features and rely heavily upon the powers of observation and correct classification in order to obtain the correct diagnosis. Both specialties are in fact complementary and closely related to each other. A fundamental understanding of dermatopathological changes is necessary if one wishes to become an effective dermatologist. In this chapter, the histopathological basic principles of the skin are discussed.