The images above are examples of Lichtenberg figures. Named after the German physicist who discovered them, these beautiful branching patterns of electricity are seen in nature in the form of lightning strikes.
The patterns above have been captured in acrylic blocks. During creation, an electron beam or particle accelerator is used to force electrons into the block, building up an electric charge. When the charge is given a release, such as the nail seen in the top picture, the electrons escape through the block to the conductor, fracturing paths through the acrylic as they travel. When finished, evidence of their course is captured in the form of the beautiful fractal creations seen above. More complex patterns, such as the butterfly and Taijitu (yin yang) symbol, require charging by two or more electron beams or multiple simultaneous points of discharge (click the images for more detail).