Ferrofluid

[Arrow]

http://www.99express.com/posts/ferrofluid_sculptures.htm

"...introduction of electro-magnetic waves into the fuid turning it solid."

[Merlion]

Thanks. It is interesting. Like many sculptures, it is suitable for placing at high-class indoor spaces like hotels to make the spaces more attractive.

More than one websites listed at the left-hand side of the homepage explain how ferrofluid works.

This paragraph taken from here (http://www.wisegeek.com/what-is-ferrofluid.htm?referrer=adwords_campaign=ferroflui d_ad=018431&_content_kw=magnetic%20fluid) explains this.
"When many people use the term ferrofluid, they are also referring to magnetorheological fluid, a fluid similar in all ways to a ferrofluid, except that the size of the (magnetic) particles is larger. This difference in size means that the fluid becomes solid when exposed to a magnetic field, then reverts to a fluid when the magnetic field is removed."

Much more details can be found here (http://en.wikipedia.org/wiki/Magnetorheological_fluid) in Wikipedia, including how to home make such fluids !