Biological signal transduction is conducted frequently at very fine cell structure expressing nano-level compartments. Up to this point, however, physiological experiments treating such fine structure are limited, mainly because of technical limitations. To overcome difficulties, we employed a combined a patch clamp and photolysis of caged compound under fine visualization of sub-micron structure with the laser-scanning confocal microscope. We used olfactory cilia as an example having 100 nm diameter structures. Our aim is to obtain real time dynamics of molecular elements in living cell with a high spatial resolution. Cilia were loaded with both caged cAMP for photolysis and lucifer yellow for luminescent visualization. When the laser light for photolysis is collected at the focal plane with the objective lens, the size (D) of the laser spot is determined following the relation, D ∝λ/NA. To obtain a small spot for a high spatial resolution, we used a objective lens having a large NA (1.4) and a short wavelength light (λ=364 nm). If the intensity of the UV spot is assumed to express spatially a two-dimensional Gaussian distribution, σ was estimated experimentally to be <300 nm. The On-Off and position of the UV spot were regulated by AOTF device and Galvano-mirror. When the local area (ca. 1 μm length) of cilium was illuminated under the whole-cell voltage clamp(-50 mV), the cell showed an inward current response of ∼10 pA, caused by the local and sudden increase of the cytoplasmic cAMP. We describe response generation, adaptation, kinetics and spatial distribution of the cAMP-triggered machinery. [J Physiol Sci. 2007;57 Suppl:S107]