Langmuir-Blodgett monolayers are studied using near field fluorescence microscopy. The setup is equipped with a feed back system based on shear force detection of the oscillating near field probe that allows optical characterization in air as well as in aqueous environments. In the monolayer liquid condensed star-shaped domains are present in a fluorophore-doped liquid expanded phase. The boundary lines between the two phases show a width of 91 nm. Observations in water give the same quality of the optical data and allow the measurement of the boundary line width with the same optical resolution. The height data at constant amplitude of the probe vibration revealed topographical contrast inversion when scanning over the boundary lines of the monolayer in water with respect to scanning in air. This setup is suited to study optical properties of complex biological systems in an aqueous environment.