Ferro Fluid - amazing liquid
A ferro fluid is, well, watch the video and read the description under it while you watch:
definition “A fluid in which fine particles of iron, magnetite or cobalt are suspended, typically in an oil.” (from webopedia, and they were invented by NASA. Answers.com defines it as “A colloidal suspension that becomes magnetized in a magnetic field because of a disperse phase consisting of ferromagnetic or ferrimagnetic particles. “