Cosmic Eye Rheoscopic Device https://www.physicsfunshop.com/search?keywords=cosmic eye visualizing the invisible- where suspended microscopic flat crystals reflect light and allow visualization of the fluid's motion. This rheoscopic fluid is special in that the suspended microscopic particles are slightly ferromagnetic and will align with any external magnetic field that is brought near the device. A small magnet within allows interesting interactions as well. From creator and artist Robert Spil