Reaction–diffusion

Reaction-diffusion is like mixing colors of paint, but instead of colors we use chemicals. Imagine you have a box with white paper and you pour some red paint in the middle of it. The red paint will start spreading slowly to the sides of the box. This is similar to diffusion, where a substance begins to move from an area of high concentration to an area of low concentration.

Now, let's say you add some blue paint to the white paper, but not in the same place as the red. The blue paint will also start spreading, but it will not mix with the red paint. This is similar to reactions, where chemicals react with each other but not with other chemicals.

But what happens when the red and blue paints meet? Depending on the type of chemical they are, they might react with each other and create a new color, like purple. This is what reaction-diffusion is all about: the combination of diffusion and reactions to create patterns and structures in nature, like the spots on a leopard or the stripes on a zebra.