Cervical cancer cell. Coloured scanning electron micrograph (SEM) of a cultured cancer cell (HeLa cells) from a human cervix, showing numerous small vesicles characteristic of cancer cells about to divide. 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. This is a control (untreated) cancer cell from an experiment to culture cancer cells with a chemotherapy drug doxorubicin to investigate cell death. Doxorubicin is a type of chemotherapy drug called an anthracycline. It slows or stops the growth of cancer cells in part by blocking an enzyme called topoisomerase 2. All cells need this enzyme to divide and renew. Magnification: x6000 when printed 10 centimetres wide. Specimen courtesy of Professor Greg Towers, University College London, UK. For a set of images showing the treated cells see C058/5931 to C058/5967.