ananyo writes "The highest possible resolution images — about 100,000 dots per inch — have been achieved, and in full-colour, with a printing method that uses tiny pillars a few tens of nanometres tall. The method could be used to print tiny watermarks or secret messages for security purposes, and to make high-density data-storage discs. Each pixel in these ultra-resolution images is made up of four nanoscale posts capped with silver and gold nanodisks. By varying the diameters of the structures (which are tens of nanometres) and the spaces between them, it's possible to control what colour of light they reflect. As a proof of principle, researchers printed a 50×50-micrometre version of the 'Lena' test image, a richly coloured portrait of a woman that is commonly used as a printing standard (abstract). Even under the best microscope, optical images have an ultimate resolution limit, and this method hits it."