A three-dimensional hologram-like image that users can reach out and touch has been achieved for the first time, using hundreds of silent speakers to levitate tiny particles of polystyrene. Creating an effect much like the displays seen in science-fiction movies such as Star Wars, the technology, inspired by the movies, is a step into the imagined future. Researchers at the University of Sussex, UK, built the'hologram' producing machine from 512 speakers set into a plinth above and below where the image appears. Ultrasound is emitted by the speakers, lifting tiny balls of polystyrene precisely into position by manipulating the sound waves - to'trap the particles acoustically'. By controlling and shifting air pressure using the speakers the balls can be so quickly manoeuvred to trace a 3D shape that they appear to be a 3D moving image - they float in pockets of low pressure created by the ultrasound. The tracing of the 3D shape desired by the polystyrene balls must be done in less than 0.1 seconds in order for the visual effect to materialise.