The sciences of complexity work toward linking traditional sciences vertically, across levels of description, and horizontally, across different domains. One fruitful move is to look at global complex phenomena which emerges from the interaction of a multitude of simple individuals. Such phenomena occur in many fields and at many levels of description, such as when ants interact to form a colony, or water molecules interact to form a fluid. To make a good model which pertains to all of these systems one must abstract common features, and render them accessible to analysis and experiment.
Cellular automata are one such good model.
In a cellular automaton the individuals are entities which have a finite number of states. These individuals are referred to as cells. We will typically be thinking of states abstractly, with labels . Applications in the natural sciences require assigning meanings to the cells and their states. This representation of an individual is among the simplest imaginable.