Imaging Ca microdomains linked to a specific molecule Summary: Intracellular Ca2+ is a second messenger in a number of cellular reactions (metabolism, gene expression, vesicular trafficking…). This signalling is made specific through Ca gradients highly localized and of very short life time (ms). Ca sensitive dyes has disclosed the existence of Ca transients, but their exact amplitudes and their precise localization is still unknown. Two reasons lag behind it: the number of Ca sensing molecule in the vicinity of the molecules of interest can be low in respect to the number of divalent cations accumulating at the intracellular mouth of a channel receptor such as NMDAR for instance. In addition, ions and dyes gradients collapse quickly due to diffusion. Our aim has been therefore to concentrate Ca sensitive molecules at the surface of a slowly diffusing molecule (here a Q Dot) with the idea to ultimately fix it on an antigenic epitope of the molecule of interest. The use of QDots as cargo molecules may make it possible to localise the nanobiosensor, in the green, while simultaneously exciting by FRET the dye, itself emitting in the red.