Human papillomavirus particles. Coloured transmission electron micrograph (TEM) of particles (brown) of the human papillomavirus (HPV) being shed from a human wart. HPV is the cause of warts, growths that are commonly found on the hands, the soles of the feet, the body's mucous membranes and also on the genitals. HPV has also been linked with some skin and cervical cancers. The surface of a wart can break off in flakes of wart cells, as seen here, releasing particles of the virus. These released particles can cause a wart on another area of skin, or on a different host. Magnification: x56,000 when printed 10cm high.