Colon goblet cells. Coloured scanning electron micrograph (SEM) of a biopsy from a child's colon (large intestine) showing a crypt of Lieberkuhn, a large pit in the intestinal wall. Within the crypt are mucus-secreting goblet cells (green). The colon starts at the small intestine and ends at the rectum. The main function of the large intestine is to reabsorb water from the faeces. Magnification: x1,500 when printed at 10 centimetres wide.