From ancient times to the present, there is no person who does not have a small mole on his or her body, and there is even evidence that the number of pigmented moles in the whole body among Asians should be more than one hundred. Many people take it for granted and give good meanings to the moles that grow in some special parts, such as those between the eyebrow arch are called “beauty moles”, those around the mouth are commonly called “mouth blessings” and so on. So what exactly is a black pigmented mole? 1.Classification of nevus nigricans: nests of melanocytes are located in the dermis. The lesions are mostly round, higher than the skin surface, with smooth surface, and may have body hair (nevus nigricans). It is the most common nevus in adults. Junctional nevus: The lesion is located at the junction of epidermis and dermis. They are usually round or oval papules with clear borders, light brown or black, without hair. Most of them transform into intradermal nevi with age. However, junctional nevi located on the palms of the hands, soles of the feet and external genitalia will always maintain the junctional characteristics and are prone to malignant transformation. Mixed nevus: It has the characteristics of both intradermal nevus and junctional nevus. The lesion is mostly brown or black, smooth or slightly protruding from the skin surface, often with hair, and surrounded by diffuse hypopigmentation. 2.Microstructure The development of light microscopy, electron microscopy and immunohistochemistry technology has led to a deeper understanding of nevus nigricans. In the past, melanin granules were not visible under light microscopy because the melanin system was in a quiescent state or the activity was weak. However, under electron microscopy, it was found that all nevus cells had tyrosinase activity of varying strength and the basic structure of melanosomes; the internal organelles (mitochondria and Golgi apparatus) of nevus cells were the same as those of melanocytes; nevus cells were in a free state without bridging granule connection. 3.Laser treatment Prognosis Laser treatment of nevus nigricans will have a natural recovery process. After the operation, there may be black scorch on the trauma surface initially, and after 1-3 days, there will be slight redness and exudation on the trauma surface, and a few blisters can be seen, and then the scabs will be dried and healed after 7 to 10 days.