False-colour scanning electron micrograph (SEM) of the transition zone between the small intestine (ileum, blue) and large intestine (caecum, green). At above centre, the ileum wall is pleated with plicae and smaller finger-like villi. These folds increase the surface area of the small intestine for its role in food digestion and absorption. Digested food is absorbed into the blood through capillaries in each villus. By contrast the caecum wall is flat, with many openings to mucous glands. In the large intestine, faeces form by absorption of excess water while mucous lubricates their path. Magnification: x100 at 6x7cm size. Magnification: x160 at 4x5 inch size.