Researchers at the wind tunnel are using soap bubbles to chart air currents. Two decades ago, American researchers attempted to do so, only to conclude that the helium-filled soap bubbles had not followed the air current with sufficient precision. As a result, the method was written off. Prof. Fulvio Scarano and Dr Andrea Sciacchitano of the AE faculty are now using very tiny bubbles (0.1 mm) that do remain captive in the air current. Thanks to the laser light reflected by the bubbles a very precise 3D record can be made of the air current. Until recently, this technology (particle image velocimetry, or PIV) was restricted to volumes equivalent to the size of an iPhone. It can now accommodate volumes up to the size of a beer crate.