Capillary endothelial cells from mammalian cardiac muscle caught in the act of fluid-phase micropinocytosis. Arrows indicate multiple sites where invaginaton along the membrane suggests vesicles forming during an endocytic event. Figure 52 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.