Nanosized sensors enable the study of chemical and biochemical processes at a level and in dimensions that may not have been envisioned some 20 years ago. Fueled by their inherent small size and the unusual optical, magnetic, catalytic, and mechanical properties of nanoparticles, remarkable progress has been made in recent years in the development and utilization of nanosensors and optical nanotechnology will further widen the field. However, the design of new sensors requires new materials, new methods for their characterization, new optical sensing schemes, new approaches for creating...