Visualizing the molecular architecture of the cell. A transmission EM image of a platinum replica of the inner plasma membrane of a HeLa cell. Many cellular features can be seen, including clathrin-coated pits and plaques, caveolae, the actin cortex, microtubules, and other vesicles. Although we know many of the molecular components (depicted in the schematics), a complete molecular cartography of the plasma membrane would identify the location, structure, and relationships of all proteins that make up the diverse features of even this small region of the cell. Bar, 77 nm. Transmission EM image courtesy of Kem Sochacki (National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD).