Electron micrograph of epithelial cells of the parotid gland of the gerbil, prepared by rapid freezing and freeze substitution. Microvilli and microplicae, which expand the extracellular surface along intercellular junctions, are particularly apparent when preserved by rapid freezing. Image by Atsushi Ichikawa, Figure 44 from Chapter 2 (Specializations of the Free Surface) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the accompanying chapter is available on the ASCB’s BioEDUCATE website.