Pigmentation refers to coloring. Pigmentation in skin takes place when a particular type of cells called melanocytes which are contained in the skin produce a pigment called melanin. The skin undergoes pigmentation depending upon the amount produced. If your body produces very little or too little melanin, hypopigmentation takes place, making your skin lighter. Vitiligo is one such condition of hypopigmentation. Hyperpigmentation occurs when your body produces excess of melanin which causes dark spots on the skin. Your skin can get darker due to pregnancy, Addison’s disease and sun exposure.