GOOD as modern display screens are, they could be a lot better. Even the best liquid-crystal display (LCD) can produce only about a third of the range of colours which the human eye (in collaboration with the brain) can perceive. But that may soon change, with the deployment in screens of structures called quantum dots.

A quantum dot is a semiconductor crystal a few nanometres (billionths of a metre) across—about 50 atoms wide, in other words. When excited, such crystals emit light. The wavelength, and hence the colour, of this light depends on the size of the dot. Large ones emit long wavelengths (red light). Small ones emit shorter wavelengths (blue). Those in between fill in the spectrum with colours such as green. The plan is to use this property to generate nuances of colour that are beyond the range of existing LCDs.