Creatine crystals, differential interference contrast light micrograph. The branched fractal structure seen here has formed due to random motions of the crystallizing molecules undergoing Brownian motion in the liquid solvent. This self-assembly process is called diffusion limited aggregation (DLA). The colours in the image are a result of thin film interference. Creatine is a nitrogeneous organic acid that occurs naturally in vertebrates. It helps to supply energy to all body cells. Magnification: x25 when printed at 10 centimetres wide.