Platinum replica electron micrographs of unroofed cells. (a) An entire HeLa cell plasma membrane showing (1) the inner surface of the plasma membrane and (2) outside the cell. (b) Zoomed view of an unroofed HeLa cell showing the (1) outer surface of the plasma membrane and (2) inner surface of the plasma membrane. (c) Zoomed view of a HeLa cell plasma membrane showing (1) clathrin-coated sites and (2) the actin cortex. (d) Image of a U-87 glioblastoma cell plasma membrane with numerous (1) caveolae. Cells were prepared and imaged using methods similar to those described previously (Sochacki et al., 2012, 2017).