Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Birthmarks ?
    ### Response:
    Birthmarks are abnormalities of the skin that are present when a baby is born. There are two types of birthmarks. Vascular birthmarks are made up of blood vessels that haven't formed correctly. They are usually red. Two types of vascular birthmarks are hemangiomas and port-wine stains.
    