Nevus is a more common skin disease. According to the different levels of melanocyte distribution in the skin, nevi are classified as junctional nevus, intradermal nevus and mixed nevus. Junctional nevus: melanocytes are distributed at the junction of epidermis and dermis. This is the early developmental stage of nevus, and most of them appear in infancy or childhood, manifesting as well-defined, light brown or black patches, mostly within 0.6-0.8 cm in diameter, with round or elliptical lesions, smooth edges and no hair. Crossborder nevi can occur in any part of the skin and mucous membranes. Almost all nevi occurring on the palms of hands, toes and vulva are junctional nevi, which have the tendency of malignant transformation. Intradermal nevus: The lesion is located within the dermis. It is a common type of adult nevus. They appear as small hemispherical elevated dermal, light brown or skin-colored swellings, mostly within 1 cm in diameter, with smooth surface and sometimes hair in the center. No clinical reports of malignant transformation of intradermal nevus have been seen. Mixed nevus: It has the characteristics of both junctional nevus and intradermal nevus. It is a transitional manifestation of the evolution of junctional nevus to intradermal nevus, mostly seen in middle-aged and young people, which is a brown to black papule with clear boundaries, often with hair, and surrounded by diffuse hypopigmentation. Treatment of nevus: surgical treatment, non-surgical treatment (laser, chemical peeling, etc.)