One of the rapidly advancing femtosecond laser technologies is three-dimensional micro- and nanostructuring by two-photon polymerization (2PP) technique. This technique allows the fabrication of any computer-generated 3D structure by direct laser {\textquotedbl}recording"into the volume of a photosensitive material. Because of the threshold behavior and nonlinear nature of the 2PP process, a resolution beyond the diffraction limit can be realized by controlling the laser pulse energy and number of applied pulses. Many different applications of 2PP technique are discussed.