Near-field optical microscopy as a prime example of a subdiffraction imaging technique is described, and various modes of its operation are discussed. These include amplitude, phase and polarization, as well as fluorescence and photoluminescence imaging and spectroscopy. Representative examples are given to indicate the performance. The application of the technique to microscopic studies of silver halide is presented in some detail. The potential of the technique in various applications is critically assessed, and future prospects are discussed.