Scanning electron micrograph showing in vitro fertilization of a hamster oocyte. The sperm head, near the center of the field of view, is engulfed by the microvilli on the surface of the oocyte membrane; the sperm tail extends to the left. Image by David Phillips, Figure 32 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.