Particles in an MR fluid undergoing structural evolution while an alternating magnetic field is applied. The far left image shows the fluid after 1 second of exposure to a high-frequency-pulsed magnetic field. The suspended particles form a strong network. Images to the right show the fluid after 3 minutes, 15 minutes, and 1 hour of exposure. Click the image to expand. The particles have formed aggregates that offer little structural support and are in the lowest energy state.