A real-life "tractor beam", which uses light to attract objects, has been developed by scientists.It is hoped it could have medical applications by targeting and attracting individual cells.
The research, published in Nature Photonics and led by the University of St Andrews, is limited to moving microscopic particles.
In science fiction programmes such as Star Trek, tractor beams are used to move much more massive objects.
In 2011, researchers from China and Hong Kong showed how it might be done with laser beams of a specific shape - and the US space agency Nasa has even funded a studyto examine how the technique might help with manipulating samples in space.
The new study's lead researcher Dr Tomas Cizmar, research fellow in the School of Medicine at the University of St Andrews, said while the technique is very new, it had huge potential.
He said: "The practical applications could be very great, very exciting. The tractor beam is very selective in the properties of the particles it acts on, so you could pick up specific particles in a mixture."
"Eventually this could be used to separate white blood cells, for example."
Usually when microscopic objects are hit by a beam of light, they are forced along the direction of the beam by the light photons. That radiation force was first identified by the German astronomer Johannes Kepler in 1619 when he observed that tails of comets always point away from the Sun.