Colon cancer. Coloured Scanning Electron Micrograph (SEM) of the inner surface of the human colon (large intestine) diseased with cancer. The diseased surface of the colon (yellow) is irregular, with an abnormal bumpy appearance caused by chaotic cell growth. This is typical of malignant and uncontrolled cancerous growth. Blood cells are red; mucus secretion is blue; scattered bacteria are green. Cancer of the colon is one of the most common cancers, especially in Western countries. Symptoms include blood in the faeces, constipation or diarrhoea, and abdominal pain. Treatment often involves surgery and anti-cancer drugs. Magnification: ×400 at 6×4.5cm size. Cover credit: Eye of science / science photo library.