Scanning electron micrograph of the epidermal surface of lamprey larvae. A row of microvilli outline the polygonal borders between cells, while short microvilli cover the external surface in a reticular network. Image from Fahrenbach, W. (1975) J. Invest. Dermatol. 65:39-44, reprinted with permission as Figure 43 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.