That reminds me of bismuth crystals:

http://www.google.co.uk/images?hl=en&source=imghp&q=...

I think that is a result of it being one of the few substances other that water that has a liquid phase that is denser than the solid.

See also MIT's work on this: http://projects.csail.mit.edu/emergentDesign/genr8/

This uses grammatical evolution, which is basically evolutionary computation guided by a grammar. The Maya plugin GENR8 was originally implemented is available for download on their website under an unclear license (assume it's restrictive).

I don't know what it is, but there is something kind of strange and gross about these sculptures. I'm not sure why I'm responding in that way, but I find them both fascinating and somehow disturbing, as though I'm seeing a little bit of the root of my own being, and it is mathematical and alien.

any guesses as to what 3d printer he's using?

The metal ones are certainly ProMetal, but the SLS prints are generic enough I couldn't tell you which one they were printed on specifically.