False-colour scanning electron micrograph (SEM) of a section through the glandular wall of the colon. The lattice-like wall of the mucosa (green) contains many closely packed glands (yellow), each with a central canal leading to the surface. Two types of cells are found in these glands: columnar cells involved in water absorption; goblet cells which secrete mucous. It is difficult to distin- guish cell types here. In the colon, undigestable food becomes faeces with the absorption of excess water. While mucous is needed to protect the colon surface and to lubricate the faeces as it passes along. Magnification: x350 at 6x7cm size. Magnification: x540 at 4x5 inch size.