Pancreas tissue. Transmission electron micrograph (TEM right) of part of the exocrine pancreas. Seen here are zymogen granules (cyan) and cell nuclei (blue). In the image the purple endoplasmic reticulum that fills the cytoplasm is clearly visible. Digestive enzymes are secreted in the zymogen granules, and passed to the small intestine through the pancreatic ducts. Magnification: x3000 when printed 10 centimetres high.