A nevi, commonly known as a mole, is a small, dark spot on the skin that is formed by clusters of pigment-producing cells called melanocytes. These spots can vary in color, size, and shape, and they are usually harmless. Most people have multiple moles, which can appear anywhere on the body. Moles can change over time, becoming darker or larger, and some may even disappear. While most nevi are benign, it is important to monitor them for any changes, as certain types can develop into skin cancer, such as melanoma. Regular skin checks can help identify any concerning changes early.