Method of production of a photochromic composite material, in which, starting from a photochromic ruthenium complex with nitrosyl ligand, with a silica matrix by a sol-gel process or with a biodegradable matrix, in particular of starch or of agar-agar, so that the photochromic ruthenium complex with nitrosyl ligand, in the crystalline state and in the form of nanoparticles, is inserted into the nanopores of the matrix.