Here is an animation I made from some MRI data of the brain.

The Corpus Callosum is rendered as a volume (the green suff)

The outer matter is rendered as a surface.

Horraaahh... at last a post!!

Hoorrraaahhh... 

At last a post...

I repeat myself but as promised here is a video explaining volume caustics in Maya with mentalray.

You have to register but you get access to lots of fab tutorials for all levels about CG and VFX.

http://www.escapestudios.com/free-tutorial-volume-caustics-for-the-maya-expert/

Dark Side Of The Spoon

Here is a little go at some volumetric caustics with MentalRay for Maya and a touch of dispersion.

Explanation will follow soon.