We have engineered new hybrid organic-inorganic materials through a generic and flexible preparation of stable organic nanocrystals grown in gel-glass matrixes for optics. Host matrixes display a microporous porosity from 0.7 to 1.6 nm depending on silicon alkoxydes and solvents used. Organic nanocrystals have been characterized by different coupled techniques and present average sizes from 10 to 27 nm according to dye molecules and molar concentration. When a magnetic field is applied during the nanocrystallization process, organic crystals exhibit larger average sizes due to a better molecular aggregation.