Phenanthrene is a polyaromatic hydrocarbon (PAH) formed of three fused benzene rings and which is found in both interstellar space and diesel exhaust. In chemistry it (and the related molecule phenanthroline) are used as ligands and which are typically bound to a central metal atom. You can find out more about this unique molecule here http://en.wikipedia.org/wiki/Phenanthrene
The basic structure was designed in Sketchup and exported as an stl file. This printed from the Cupcake CNC (Makerbot) in about 18 minutes.
Conveniently the basic hexagon can also be used as the basic format for many other PAH's.