There is a growing interest in the development of submicron optochemical sensing devices. Miniaturization of sensors to nano-dimensions decreases their typical response time down to the millisecond time scale. Their penetration volume is reduced to a few cubic micrometers and they exhibit a spatial resolution at the nanometer scale. In this review the fabrication of submicron optical fiber fluorescent sensors and particle-based fluorescent nanosensors is described. The functional characteristics of these exciting miniaturized fluorescent sensors and their applications for quantitative measurement of intracellular analytes are demonstrated.