Microcapsules chromatically encoded layer by layer as libraries of combinatorial analysis and as specific optical sensors.

Capsules - with a diameter less than 100 microns, and - a casing comprising at least three polyelectrolyte layers, wherein the shell contains only one dye and at least one of these three polyelectrolyte layers being marked with the dye, which is associated in high concentration covalently with a sensitive material, wherein the sensitive material can react to conditions modified environment for volume increase or decrease in volume, - where the dye concentration is so high that the dye forms with themselves dimers, aggregates or excimer lead to an automatic fluorescence quenching or configuration of a new emission band, and - where the sensitive material is an organic polyelectrolyte.