Warts are small harmless tumors of the skin caused by a virus called the human papillomavirus.

  1. Warts occur in a variety of shapes and sizes. A wart may appear as a bump with a rough surface, or it may be flat and smooth.
  2. Tiny blood vessels (capillaries) grow into the core of the wart to supply it with blood. In both common and plantar warts, these capillaries may appear as dark dots (seeds) in the wart's center.