Most moles develop because of a harmless proliferation of pigmented cells in the deeper layers of the skin. They often form spontaneously and are worsened by exposure to UV rays or sunshine, which is why they typically manifest on the trunk, arms, or legs. Although most moles emerge before the age of 20, they do persist into the 30s and 40s. By and large, the bulk of moles fade away with age. In later age, adults often acquire non-mole growths like as freckles, lentigines, "liver spots," and seborrheic keratosis. After the age of 30, new moles may need careful monitoring, medical assessment, and, if necessary, biopsy. A newly formed mole in an adult may be the result of a developing aberrant mole or an early stage of melanoma. It is critical to have your dermatologist examine any new or changing mole.