Capillary malformations are abnormal growths of small blood vessels, often appearing as red or purple marks on the skin. These marks can vary in size and shape and are usually present at birth. They are commonly referred to as port-wine stains when they resemble the color of red wine. These malformations occur due to the improper development of capillaries, which are tiny blood vessels that supply blood to the skin. While capillary malformations are generally harmless, they can sometimes be associated with other conditions, such as Sturge-Weber syndrome, which may require further medical evaluation.