Lung cancer cells dividing, coloured scanning electron micrograph (SEM). Lung cancer occurs when abnormal cells divide in a chaotic and uncontrolled manner resulting in the formation of a tumour in the lungs. Lung cancer is the most common cause of cancer death in the UK. In 2016 it accounted for 21 per cent of all cancer deaths in the UK. In terms of survival, approximately 5 per cent will survive 10 years or more and 10 per cent will survive 5 years or more. In this image the cells are undergoing cytokinesis which is the physical process of cell division which divides the parental cell into two daughter cells. Magnification: x3000 when printed at 10cm wide.