Recent studies on the in-situ observation of the monomolecular films at the air-water interface by means of the fluorescence microscopy and the reflection spectroscopy are reviewed. Several kinds of Langmuir trough equipped with fluorescence microscope were constructed. Various morphologies and crystallization process of the surface monolayers were observed. Thermal treatment of the surface monolayer was shown to be effective for the crystal growth. Crystallization of the guest cyanine dye at the well organized charged interface of the monolayer was monitored not only by the fluorescence microscopy but also by the reflection spectroscopy.
