Figure 168 from Chapter 5 (Endoplasmic Reticulum) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. Electron micrograph of rough endoplasmic reticulum (RER) in an acinar cell from the pancreas of the small brown bat, Myotis lucifugus. The nucleus of the cell is in the upper left corner; the RER in the lower half of the micrograph is stacked in a cisternal structure, and studded with ribosomes. This cisternal packed organization is common in cells that actively produce proteins for secretion, like this acinar cell. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.