Researchers have trapped a rainbow - slowing light to a near-stop - in an array of 25,000 "invisibility cloaks", each smaller than a hair's breadth.
The trick could aid the analysis of complex samples or even communications. In recent years, a number of research efforts has demonstrated a wide range of cloaking techniques. Light can either be guided around or cancelled by a material that makes an object invisible to an observer. For the most part, such cloaks have been tiny or limited in the range of colours or angles of light they work with. Nevertheless, this kind of engineering of light and the paths it takes has in principle a great many applications besides invisibility.