The cause of most pigmented nevi is unknown and may be related to heredity or developmental defects. Among them, pigmented nevi originate from the benign proliferation of melanocytes (referred to as melanocytes), and epidermal nevi and sebaceous nevi originate from an abnormal combination of specific normal tissues. The cause of congenital nevi is unknown and may be related to genetic mutations during embryonic development. An important cause of acquired pigmented nevi is ultraviolet radiation in the environment, which may also be related to drugs, trauma, changes in hormone levels, and immunosuppression, etc. Dermal melanocytic nevi are mostly congenital, resulting from melanocytes remaining in the dermis as they move toward the epidermis during embryonic development. Dysplasia refers to the wrong combination and arrangement (increase or decrease of normal structure) of a normal tissue in the process of development of the body, which leads to tumor-like deformity. Cutaneous dysplasia refers to a large group of abnormalities of skin development, mainly changes in the epidermis, connective tissue, and appendages, such as epidermal and sebaceous nevi. Usually, nevi appear on the face, limbs, and trunk of the population, and the lesions are in the form of macules or papules with clear boundaries and regular margins. Most patients do not need to take treatment measures, if it affects aesthetics, it can be treated by surgical excision, laser and other ways. For those who have clear nevus, they can take treatment measures according to their own actual situation, pay attention to daily skin care, avoid ultraviolet irradiation, foreign body stimulation and so on.