Figure 170 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 human pancreas. The RER is stacked in a cisternal structure, and studded with ribosomes. In this particular preparation, fixation conditions were modified to preserve a flocculent precipitate of newly synthesized protein in the lumen of the ER. The nucleus of the cell is in the upper right corner. Micrograph by Susmo Ito and Arthur Like. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.