An international team of researchers led by groups from the Max Planck Institute in Marburg and the Philipps University in Marburg has stumbled upon the first regular molecular fractal in nature. They discovered a microbial enzyme—citrate synthase from a cyanobacterium—that spontaneously assembles into a pattern known as the Sierpinski triangle. Electron microscopy and evolutionary biochemistry studies indicate that this fractal may represent an evolutionary accident.