Individual lipidmovementin a monolayer is studied over long time intervals (500 s) by darkfield microscopy
of single lipids labeled with gold colloids (30 or 100 nm in diameter). Dimyristoyl phosphatidylcholine in
the fluid phase shows normal diffusion, with a diffusion coefficient of (1.1 ( 0.2)  10-8 cm2/s. Since this
is consistent with values derived from the diffusive transport of many lipids, the analysis of gold-tagged
lipids in a monolayer provides a reliable picture of lipid diffusion on the level of single molecules.