That’s not Photoshop. The Dutch artist Berndnaut Smilde has developed a way to create asmall, perfect white cloud in the middle of a room. It requires meticulous planning: the temperature, humidity and lighting all have to be just so. Once everything is ready, Smilde summons the cloud out of the air using a fog machine. It lasts only moments, but the effect is dramatic and strangely moving. It evokes both the surrealism of Magritte and the classical beauty of the old masters