Researchers have shown how the polarization of light can be controlled by a magnetic field applied to a thin film of ferrofluid (Ferrocell). They obtained patterns of polarized light with magnetic field configurations such as monopolar, tetrapolar and hexapolar, and studied how polarized light varies for different intensities and orientations of the applied magnetic field. Using the Jones calculus, researchers explored the key optical properties of this system and how these properties relate to the applied magnetic field.