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A detail of part of a complex fan blade fabricated using a wire + arc additive manufacturing process (WAAM) which deposits layers of metal from a wire in a technique derived from welding. Optical interference patterns as a result of surface oxides produce the iridescent colours. In use the metal would be finished by conventional machining to a smooth surface.The concept was first described in 1927 but developments in robotic control have now brought it to importance in the manufacture of, for instance, aircraft parts which are conventionally machined from solid blocks of metal. Times to manufacture pieces from steel, titanium, copper and other metals, alloys and composite materials is significantly shorter than using conventional methods with considerable cost savings. Photographed at Cranfield University, UK. (KEYSTONE/SCIENCE PHOTO LIBRARY/JAMES KING-HOLMES/SCIENCE PHOTO LIBRARY)