Liquid structures on solid substrates have been imaged with a resolution in the nanometer range by scanning force microscopy in the tapping mode. Using substrates with an artificially patterned wettability, characteristic features in the three-phase contact line were induced, which allow the contact line tension to be determined. The values in the range of -1 x 10(-10) N obtained for sessile droplets of hexaethylene glycol are consistent with theoretical predictions.