Electron micrograph showing fingerprint like ridges called microplicae on the surface of fish skin epidermis from the neon tetra. These ridges offer mechanical reinforcement against trauma and help hold an abundant mucous layer in place, both protective devices for the skin. Image by Nancy Alexander, Figure 40 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.