Photons are funny things. Not only do they exist as both a wave and a particle (depending on how you view them) but they also have no charge. This neutrality makes it very difficult to manipulate photons as magnetic fields cannot control them as they control electrons. At least 'real' magnetic fields cannot, but the 'synthetic' or effective magnetic fields researchers at the Stanford School of Engineering have created can.
The researchers synthesized their magnetic field with a precisely-etched piece of silicon. The cavities in the silicon cause it to act as a photonic crystal, which can already affect photons. By applying an electric current to the silicon though, a magnetic field is synthesized that exerts a virtual force on photons passing through the crystal, making them behave like electrons. This, in effect, gives the photons a charge which violates the time-reversal symmetry of light law, because when traveling backward in time, the charge will be opposite.
The possibilities for this technology are truly impressive as it may allow for devices to utilize photons similarly to how we currently use electrons. One example would be removing any reflection from a material by preventing light from traveling in a specific direction.