Turing Patterns (Reaction-Diffusion)

In 1952, Alan Turing proposed that patterns in nature (like zebra stripes or leopard spots) could emerge from two interacting chemicals: an "activator" and an "inhibitor".
The activator creates more of itself and also creates the inhibitor. The inhibitor suppresses the activator. Crucially, the inhibitor diffuses (spreads) faster than the activator.
This simple local competition creates stable, large-scale structures (spots, stripes, or labyrinths) out of random noise.