Ok I need this. This and an ingenious way to keep it safe in the form of a nice looking coffeetable piece people can play with… It’s ferrofluid… here’s the science side:

A ferrofluid is a stable colloidal suspension of sub-domain magnetic particles in a liquid carrier. The particles are about 100 Angstroms in size, and are coated with a surfactant to keep the particles from clumping together (even when a magnetic field is applied). By volume, a ferrofluid is about 5% magnetic solids, 10% surfactant, and 85% carrier. When no external magnetic field is present, the magnetic moments of the particles are random, and the fluid is not magnetic. When an external magnetic field is applied, the magnetic moments of the particles orient themselves almost instantly to the magnetic field lines of the external source. When the magnetic field is removed, the particles go back to random alignment very quickly.

A lot more amazing pictures after the jump… only 25$ for a 50mL bottle from WonderMagnet (but do pay attention to the hazards, such as to clothing and skin exposure) If anyone else was at Siggraph in SD a few years ago, i think there was an example of something similar to this in the innovative technologies section on a much larger scale, it was the booth that was always crammed with people completely mesmerized.