Two-photon polymerization is a 3D nanoscale manufacturing tool that offers great potential for rapid prototyping and the manufacture of photonic devices, tissue scaffolds and biomechanical parts. The rapid development of femtosecond laser systems and their transformation from research to production tools is triggering the industrialization of laser applications based on nonlinear optical processes, which so far have been confined to the laboratory. Direct laser writing by two-photon polymerization (2PP) of photosensitive materials is an example of such an application, and has emerged as a promising technique for rapid and flexible fabrication of fully three-dimensional (3D) structures with sub-100-nm resolution.