The term "dissipative structure" is used by the Prigogine School (from Ilya Prigogine, winner of the Nobel Prize in Chemistry) to describe emergent structures arising in self-organizing systems. Such structures are dissipative by serving to dissipate energy in the system. They happen at a critical threshold of far-from-equilibrium conditions. An example is the hexagonal convection cells that emerge in the Benard System when it is heated. Another example are the so-called chemical clocks demonstrated in the Belousov-Zhabotinsky reaction. These chemical clocks are composed of both temporal structures, such as a shift from one color to another with the regularity of a clock, and spatial structures such as spiral waves.