A method for producing a marked polymer, comprising the steps: a) mixing polymer precursors with a marker and polymerizing the polymer precursors, resulting in a marked polymer; or b) mixing a polymer with a marker, resulting in a marked polymer; wherein the marker comprises or consists of particles which comprise or consist of a metal and/or a semi-metal, the marker having at least three atomic species with a different atomic number, wherein the marker consists of particles with a particle size in the range of 500 nm to 1000 μm, measured by a microscopic imaging method, characterized in that the marker is i) geometrically modified such that it - has a geometric profile in the surface; and/or - has been processed by a method selected from the group consisting of lithography on the particles, laser beam treatment on the particles, electron beam treatment on the particles, etching and combinations thereof; and/or - has an inscribed pattern; and/or ii) is chemically modified, such that it - has been processed by a method selected from the group consisting of the covalent attachment of molecules to the particles, doping, ion implantation into the particles, attachment of nanodots to the particles and combinations thereof; and/or - comprises or consists of nanodots. a) mixing polymer precursors with a marker and polymerizing the polymer precursors, resulting in a marked polymer; or b) mixing a polymer with a marker, resulting in a marked polymer; wherein the marker comprises or consists of particles which comprise or consist of a metal and/or a semi-metal, the marker having at least three atomic species with a different atomic number, wherein the marker consists of particles with a particle size in the range of 500 nm to 1000 μm, measured by a microscopic imaging method, characterized in that the marker is i) geometrically modified such that it - has a geometric profile in the surface; and/or - has been processed by a method selected from the group consisting of lithography on the particles, laser beam treatment on the particles, electron beam treatment on the particles, etching and combinations thereof; and/or - has an inscribed pattern; and/or ii) is chemically modified, such that it - has been processed by a method selected from the group consisting of the covalent attachment of molecules to the particles, doping, ion implantation into the particles, attachment of nanodots to the particles and combinations thereof; and/or - comprises or consists of nanodots. wherein the marker comprises or consists of particles which comprise or consist of a metal and/or a semi-metal, the marker having at least three atomic species with a different atomic number, wherein the marker consists of particles with a particle size in the range of 500 nm to 1000 μm, measured by a microscopic imaging method, characterized in that the marker is i) geometrically modified such that it - has a geometric profile in the surface; and/or - has been processed by a method selected from the group consisting of lithography on the particles, laser beam treatment on the particles, electron beam treatment on the particles, etching and combinations thereof; and/or - has an inscribed pattern; and/or ii) is chemically modified, such that it - has been processed by a method selected from the group consisting of the covalent attachment of molecules to the particles, doping, ion implantation into the particles, attachment of nanodots to the particles and combinations thereof; and/or - comprises or consists of nanodots. i) geometrically modified such that it - has a geometric profile in the surface; and/or - has been processed by a method selected from the group consisting of lithography on the particles, laser beam treatment on the particles, electron beam treatment on the particles, etching and combinations thereof; and/or - has an inscribed pattern; and/or - has a geometric profile in the surface; and/or - has been processed by a method selected from the group consisting of lithography on the particles, laser beam treatment on the particles, electron beam treatment on the particles, etching and combinations thereof; and/or - has an inscribed pattern; and/or ii) is chemically modified, such that it - has been processed by a method selected from the group consisting of the covalent attachment of molecules to the particles, doping, ion implantation into the particles, attachment of nanodots to the particles and combinations thereof; and/or - comprises or consists of nanodots. - has been processed by a method selected from the group consisting of the covalent attachment of molecules to the particles, doping, ion implantation into the particles, attachment of nanodots to the particles and combinations thereof; and/or - comprises or consists of nanodots.