Pancreas tissue. Coloured scanning electron micrograph (SEM) of fractured exocrine pancreas tissue, showing numerous acinar cells, containing secretory zymogen granules. The freeze fracture has revealed larger cell nuclei (purple) and the depressions they sit in. Digestive enzymes are secreted in the zymogen granules, and passed to the small intestine through the pancreatic ducts. Magnification: x1600 when printed 10 centimetres wide.