Here, I'll help: OLD! Methuselah probably watched this in his 8th grade science class. But here it is anyway. I'm mainly posting it because ferrofluids are freaking awesome and you may not have seen them. That, and I secretly like posting old things because it reminds me of my childhood when life was carefree and I didn't have to worry about this rash.
A ferrofluid (from the Latin ferrum, meaning iron) is a liquid which becomes strongly polarized in the presence of a magnetic field. It is a colloidal mixture comprising extremely small magnetic particles suspended in a liquid. The particles are coated with a soap or detergent to prevent them from clumping together.
Basically it's a magical black liquid that makes a lot of spikies in response to magnetic stimuli and is amazing to watch.
UPDATE: I just got an email from a very reliable metal expert, and he has something he wants to say about ferrofluids.
Sent: Thurs 2008-05-01 12:58
To: Writer, The Geekologie
I really want to stick my metal rod in that ferrofluid.
Youtube (links on page to other ferrofluid videos as well)
Thanks to Amy, a rare-earth magnetic beauty herself, for the tip