# Reaction–diffusion system
## MicroSim spec
- **Recommended sim type:** reaction-diffusion
- **Microsimmability score:** 94/100
- **Layout:** drawing region (canvas) on top; control region (sliders/buttons) below.
### Parameters (tunable controls)
- `Feed rate`
- `Kill rate`
- `Diffusion ratio`
### What animates
Gray-Scott spots and stripes nucleate and spread across the canvas as feed and kill rates change.
### Learning objective
Show how reaction and diffusion together generate Turing patterns.
## Links (Wikipedia order)
<!-- injected from _registry/childlinks/Reaction–diffusion_system.json (2026-07-30T02:09:12Z) -->
`Action_potential` · `Alan_Turing` · `Ansatz` · `Autowave` · `Belousov–Zhabotinsky_reaction` · [[Bifurcation_theory]] · `Biology` · `Catalytic_converter` · `Chemical_kinetics` · `Chemical_reaction` · [[Chemistry]] · `Combustion` · `Curvature` · `Diagonal_matrix` · [[Diffusion]] · `Diffusion-controlled_reaction` · `Diffusion_equation` · `Diffusion_process` · `Dissipative_soliton` · [[Ecology]] · `Eigenfunction` · `Equivalence_class` · `FitzHugh–Nagumo_model` · `Geology` · [[Geometry]] · `Hopf_bifurcation` · `Hysteresis` · `Jack_Copeland` · `Jacobian_matrix_and_determinant` · `Jonathan_Bowen` · `Limit_cycle` · `Linear_stability` · `MClone` · `Morphogenesis` · `Multi-state_modeling_of_biomolecules` · `Oxford_University_Press` · `Parabolic_partial_differential_equation` · [[Pattern_formation]] · `Patterns_in_nature` · `Periodic_travelling_wave` · `Phase_space_method` · `Philip_Maini` · [[Physics]] · `Plane_wave` · `Population_(biology)` · `Rayleigh–Bénard_convection` · `Robin_Wilson_(mathematician)` · `Ruth_Baker` · [[Schrödinger_equation]] · [[Self-organization]] · `Self-similar_solution` · `Stochastic_geometry` · `Temperature` · `The_Chemical_Basis_of_Morphogenesis` · `The_Turing_Guide` · `Turing_pattern` · `Wave_vector` · `ZFK_equation` · `Zeldovich_number`
## From the Real GENERATIVE library (beauty pass)
*Reaction–diffusion system — animation hotlinked from Wikimedia Commons (via the Real G.E.N.E.R.A.T.I.V.E. course library, STEM and Music room). [Details & license](https://commons.wikimedia.org/wiki/File:Reaction-Diffusion.gif).*
*Reaction–diffusion system — image hotlinked from Wikimedia Commons (via the Real G.E.N.E.R.A.T.I.V.E. course library, STEM and Music room). [Details & license](https://commons.wikimedia.org/wiki/File:Travelling_wave_for_Fisher_equation.svg).*
> Reaction–diffusion systems are mathematical models that correspond to several physical phenomena. The most common is the change in space and time of the concentration of one or more chemical substances: local chemical reactions in which the substances are transformed into each other, and diffusion which causes the substances to spread out over a surface in space. ([Wikipedia](https://en.wikipedia.org/wiki/Reaction%E2%80%93diffusion_system))
<!-- BEAUTY-PASS-MEDIA:END -->
> p5.js MicroSim stub · part of Systems Thinking · [Wikipedia source](https://en.wikipedia.org/wiki/Reaction%E2%80%93diffusion_system)
> Relation: subfield of systems thinking.
## Concept summary
Reaction–[[Diffusion|diffusion]] systems are mathematical models that correspond to several physical phenomena. The most common is the change in space and time of the concentration of one or more chemical substances: local chemical reactions in which the substances are transformed into each other, and diffusion ...
## Build checklist
- [ ] Claim it: set `status: in-progress` + `lease` + `leased_at`
- [ ] Write the child page explaining the concept (tie it back to systems thinking)
- [ ] Finalize parameter ranges and defaults
- [ ] Implement the p5.js sketch (drawing + control regions)
- [ ] Add caption + the learning objective on the page
- [ ] Set `status: done`
## p5.js sketch
```javascript
// MicroSim: Reaction–diffusion system
let controls = {};
function setup() {
// createCanvas(...); create sliders for the parameters above.
}
function draw() {
// background(...); read controls; render reaction-diffusion; respond live.
}
```
---
Back to Systems Thinking · Wikipedia: [Reaction–diffusion system](https://en.wikipedia.org/wiki/Reaction%E2%80%93diffusion_system)
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## Semiotic profile
> *The semiotic universals this article invokes, machine-derived from the crossref — **unverified** (born so). Populated 2026-07-06 for the Systems room.*
**Universals (6):** 🟢 diffusion (28) · 🟡 system (20) · 🟡 science (5) · 🟢 emergence (1) · 🟢 spiral (1) · 🟢 transformation (1)
**Enter by sign:** Systems Semiotic Gateway · Alphabetum · Icon Registry · ← Systems Portal
<!-- SEMIOTIC-PROFILE:END -->
<!-- BEAUTY-PASS-MEDIA:START -->
## Wikipedia : Wikitube
**Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Reaction–diffusion_system) : [Wikitube](https://en.wikitube.io/wiki/Reaction–diffusion_system)
## Previous hub tags
Tree parents: [[Cellular_automaton]] · [[Complex_system]] · [[Cybernetics]] · [[Emergence]] · [[Feedback]] · [[Self-organization]] · [[Systems_science]] · [[Systems_theory]].
Legacy hubs: none.
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*Sources: 2 legacy notes. Minted wave 1, 2026-07-30 (v1.6 order).*