Left A 3nm x 3nm image of docosanol taken at the liquid-solid interface on graphite. The black bar is superimposed over one molecular length, measured to be 3.0 + 0.2nm. The left-hand trough (marked in the image) signifies the alcohol group, which show up slightly darker relative to the rest of the hydrocarbon chain. The individual bright (yellow) spots along the molecular axis depict individual hydrogen atoms. You can actually count them and get 22 hydrogens per molecule (only one hydrogen per carbon is visible to the STM since the second hydrogen on each carbon is pointing down into the graphite and therefore not seen in the image).