Cellular automaton

A cellular automaton is a model used in computer science and mathematics. The idea is to model a dynamic system by using a number of cells. Each cell has one of many possible states. With each "turn" or iteration the state of the current cell is determined by two things: its current state, and the states of the neighbouring cells. 
A very famous example of a cellular automaton is Conway's Game of Life. Stanislaw Ulam and John von Neumann first described cellular automata in the 1940s. Conway's Game of Life was first shown in the 1970s. 
Biology.
Some things in nature happen because of cellular automata.
The patterns of certain seashells are made by natural cellular automata. Examples can be seen in the genera "Conus" and "Cymbiola". The pigment cells are in a narrow band on the shell's lip. Each cell secretes pigments based on what pigment cells around it are doing. The cell band leaves the colored pattern on the shell as it slowly grows. For example, the species "Conus textile" has a pattern that looks similar to Wolfram's rule 30 cellular automaton.
Plants control how much gas they have with a cellular automaton. Each stoma on the leaf acts as a cell.
Moving wave patterns on the skin of cephalopods can be simulated with a two-state, two-dimensional cellular automata, each state corresponding to either an expanded or retracted chromatophore.
Threshold automata have been made to act similar to neurons. These can do complex things, such as recognition and learning.
Fibroblasts are similar to cellular automata. This is because each fibroblast only interacts with others next to it.