Cervical cancer cells. Coloured scanning electron micrograph (SEM) of cultured cancer cells (HeLa cells) from a human cervix, showing numerous microvilli and dividing cells characteristic of cancer cells. HeLa cells are a continuously cultured cell line of immortal human cancer cells. As they are immortal they thrive in the laboratory and are widely used in biological and medical research. Cancer of the cervix (the neck of the uterus) is one of the most common cancers affecting women. Magnification: x1000 when printed 10 centimetres wide.