A mole on the skin is a normal skin growth that develops when pigment-producing cells (melanocytes) grow in groups. They can appear as small, dark marks, or sometimes flesh-colored small bumps, on your skin. Most people have around 10 to 40 moles that appear during childhood and adolescence and may change in appearance or fade over time. Moles can appear anywhere on your skin or mucous membranes, alone or in groups. They can be smooth, wrinkled, flat, or raised, and may have hair growing from them. Most moles are oval or round and are usually less than 1/4 inch (about 6 millimeters) in diameter, which is the size of a pencil eraser. Moles can develop anywhere on your body, including your scalp, armpits, under your nails, and between your fingers and toes. There are different types of moles, including common moles, atypical moles, and congenital melanocytic nevi. Most moles are harmless, but some types can develop into skin cancer. It is important to get to know your skin and check it regularly for changes in color, size, shape, or texture, and to see a dermatologist if you notice any unusual changes.