Alan Turing's 1952 paper "The Chemical Basis of Morphogenesis" showed that two diffusing chemicals — activator (u) and inhibitor (v) — can spontaneously break symmetry and form stable patterns. The Gray-Scott model: ∂u/∂t = Du∇²u − uv² + F(1−u); ∂v/∂t = Dv∇²v + uv² − (F+k)v. Spots form when Du>>Dv; stripes when diffusion rates are closer. Actual animal coat patterns match specific parameter regimes — spotted leopards, striped zebras, and labyrinthine cow markings all emerge from the same equations.
Morpho butterfly wings contain no blue pigment — color arises from thin-film interference in layered chitin nanostructures (~200 nm spacing). At angle θ, constructive interference for wavelength λ = 2nd·cos(θ) where n is refractive index and d is layer spacing. This produces brilliant, angle-dependent color. Peacock feathers use 2D photonic crystals (melanin rods in protein matrix). Cephalopods (squid, octopus) have chromatophores + iridophores for active, millisecond color change — structural and pigment-based simultaneously.