TECHNOLOGY FOCUS - POLYMERS - Preferred Parameters: The shell comprises semicrystalline cellulose nanofibers and/or cellulose nanocrystals having a crystallinity index of at least 40%, preferably at least 50%, more preferably at least 55%, still more preferably of at least 60% and most preferably of at least 70%. The longest dimension of the shell is at most 1 cm, preferably 0.1-5 mu m, more preferably 0.6-4 mu m and most preferably 1-2 mu m. The cellulose nanofibers have an average length of 1-5000 nm, preferably 1-1000 nm, more preferably 50-1000 nm, even more preferably 150-600 nm and most preferably 250-500 nm, and/or, where the cellulose nanocrystals have an average length of 40-2000 nm, preferably 60-2000 nm, more preferably 80-2000 nm and most preferably not greater than 100-2000 nm. The cellulose nanofibers and/or cellulose nanocrystals have an average aspect ratio of 5-1000, preferably 10-150, more preferably 30-100 and most preferably 50-80. The shell of the capsule has an elastic modulus of at least 1 GPa, preferably of at least 2 GPa, more preferably of at least 3 GPa, more preferably of at least 4.5 GPa, still more preferably of at least 10 GPa, still more preferably of at least 20 GPa and most preferably of at least 138 GPa. Preferred Components: The semicrystalline cellulose nanofibers and/or cellulose nanocrystals are in the form of a three-dimensional network, in which at least some of the semicrystalline cellulose nanofibers and/or cellulose nanocrystals are connected with one or more other semicrystalline cellulose nanofibers and/or cellulose nanocrystals of the shell of the capsule, preferably by any bond selected from covalent bonds, ionic bonds, physical bonds and its combinations. The shell further comprises an oligomer and/or a polymer, which is preferably selected from polyureas, polyurethanes, polyacrylates, polymethacrylates, polyethers, polyamides and arbitrary combinations of two or more of the polymers. The core of the capsule contains as target compound any compound selected from fats, oils, colloids, drugs, food ingredients, micelles, dyes and arbitrary combinations of two or more of the compounds. The target compound is compound which has a triplet state capable of energy transfer via an emissive process or a non-emissive process, and preferably is: (i) phosphorescent compound; or (ii) a mixture of sensitizer compound being capable of absorbing radiation at a first frequency v1 and of emissive compound, where the sensitizer compound is capable of transferring energy to the emissive compound and where the emissive compound, after obtaining energy transferred from the sensitizer compound, is capable of emitting light at a second frequency v2, where the following equation is fulfilled: v2 not greater than v1, where the sensitizer compound is capable of a triplet-triplet energy transfer to the emissive compound and where the emissive compound is capable of a triplet-triplet annihilation. Preferred Composition: The weight ratio of semicrystalline cellulose nanofibers and/or cellulose nanocrystals to oligomer and/or polymer in the shell amounts to 100:0.1 to 0.1:99.9, preferably 80:20 to 10:90 and most preferably 70:30 to 14:86. EXAMPLE - No suitable example given.