Diffusion normally smoothes out concentration gradients, but Turing showed that differential diffusion can drive the formation of stationary patterns of activator and inhibitor (Fig. 1a ...

Figure 1: a) Stationary diffraction pattern of cBN powder, integrated over the Debye-Scherrer rings, measured with femtosecond x-ray pulses as a function of the diffraction angle 2θ. b ...