3-D printing by direct laser writing produces micrometer-sized structures with precisely defined properties. Researchers of Karlsruhe Institute of Technology (KIT) have now developed a method to erase the ink used for 3-D printing. In this way, the small structures of up to 100 nm in size can be erased and rewritten repeatedly. One nanometer corresponds to one millionth of a millimeter. This development opens up many new applications of 3-D fabrication in biology or materials sciences, for instance.