After years of science fiction speculation and scientific experimentation, researchers have created a working tractor beam. The newly invented tractor beam only works on microscopic particles, but in a recent paper in Nature Photonics, scientists at Scotland's University of St. Andrews and the Czech Republic Institute of Scientific Instruments explain that the discovery could have a variety of medical applications.
Light has the power to push particles, as Johanes Kepler determined when he observed that the tails of comets point away from the sun. However, scientists have discovered that there's a very small window in which this principle reverses, and light attracts certain microscopic particles instead. The principle's reversal depends on the size and composition of the particles being attracted, which means that this technology could be used to sort specific cells — you can see an example in the video below.
Unfortunately, we're a long way off from a Star Trek scale tractor beam. Lead researcher Tomas Cizmar explained to the BBC that because the microscopic tractor beam transfers energy, "it would result in a massive amount of heating of an object, like a space shuttle. So trapping a space ship is out of the question."