Plantar Warts are benign growths on the bottom of the foot caused by a virus called the human papillomavirus (HPV). This virus enters the skin through small or invisible cuts. The wart develops in the outer layer of the skin and is typically covered with a layer of callus tissue. Sometimes small black dots are visible. These are blood vessels that grow within the wart. Over time, the wart can grow and other warts can emerge that sometime coalesce into a larger cluster called a mosaic wart. Although warts are generally harmless, they can be quite painful when present on weight-bearing areas of the foot.