Summary form only given. Current progress in the instrumentation and measurements of NSOM is described. The most critical element in NSOM is an aperture probe, which is a tapered and metal-coated optical fiber. The design and fabrication of the probe are examined with regard to aperture quality and the efficiency of light propagation. The recent dramatic improvements in spatial resolution and optical throughput are illustrated by selected applications, Raman spectroscopy, polarization microscopy, and the emission imaging of semiconductor nanostructures and single molecules. Real-space mapping of exciton wavefunctions confined in a quantum dot is also demonstrated as an application of NSOM to wavefunction engineering.