When items are printed using the new technology, they're made up of voxels (three-dimensional pixels) that incorporate either red, yellow or blue light-sensitive dye. All of the voxels take on their colors when the object is exposed to ultraviolet light. Even after being removed from the UV light, all of the voxels remain "switched on," so the object is a mosaic of red, yellow and blue. The dye, however, can be "switched off" and made transparent when exposed to sufficiently-intense visible light. With this in mind, after all of the voxels have been switched on using UV light, some of them are then selectively switched off by projecting a pattern of visible light onto the object. [Source]