Moles are tiny, round and dark colored growths on skin that can grow on any part of the body. Their size could be between a few millimeters and up to an inch. They are known as nevus in the medical terminology.

Moles start with the uneven growth of skin cells called melanocytes that are responsible for pigmentation. These melanocytes start to grow in clusters instead of being evenly spread out on the skin. There are several reasons behind moles like genetics as many are born with moles. Moles are more common in females so there could be a link between the female hormones and the moles. Probably that is why moles grow or increase size during pregnancy. Over exposure to sun can also cause moles.