I just learned about Ferrofluid today. It can do some amazing things, like this video shows. After the jump is a second video explaining HOW ferrofluid works.
From the YouTube descriptioin:
A steel sculpture with changing magnetisation is coated with ferrofluid.
The fluid is pulled in the direction of increasing flux density and forms peaks, which become smaller in higher flux density. At an accumulation of fluid at ridges, the flux density at the surface decreases. The flow and the distribution of the fluid can be observed at several characteristic locations…
The centre part of the sculpture is a conical spiral that has one, three or even more tracks of peaks depending on the magnetisation. Further tracks are built at the crown and at the ridge of the central hexagon.
The crown has horizontal cavities that discontinue the gradient of flux density. On the way to the top the fluid is accumulated until the cavities are bridged by fountains. On the way back the fluid falls in large drops over the gap.
The horizontal cavity at the ridge of the hexagon remains filled at the retreat. With increasing magnetisation the fluid at the ridge rises steeply as the flux density on the hexagon is slightly higher than at the other side of the cavity.
One can also just enjoy looking at the movements of the object.
Ferrofluid is an assemblage of magnetic particles engineered at the nanoscale, 100 times smaller than the wavelength visible light. Although too small to be imaged with microscopes, nano-products harness surprising properties from nanoscale physics for use in the macroscale world.