I've previously discussed polymers. A polymer is a long chain made up of repeated molecules linked together. The plastic that makes up LEGO bricks is ABS, a compound polymer made of three different parts. Nathan Proudlove was originally going to produce all of these in brick form, but due to the size of the project limited himself to a beautiful rendition of acrylonitrile. The black spheres represent carbon atoms, the white are hydrogens, and the blue sphere is a nitrogen. You can also see that two of the carbons are connected by a double bond (two pairs of shared electrons), and the carbon and nitrogen are connected by a triple bond (three pairs).