<P> One example of complex system whose emergent properties have been studied extensively is cellular automata . In a cellular automaton, a grid of cells, each having one of finitely many states, evolves over time according to a simple set of rules . These rules guide the "interactions" of each cell with its neighbors . Although the rules are only defined locally, they have been shown capable of producing globally interesting behavior, for example in Conway's Game of Life . </P> <P> When emergence describes the appearance of unplanned order, it is spontaneous order (in the social sciences) or self - organization (in physical sciences). Spontaneous order can be seen in herd behavior, whereby a group of individuals coordinates their actions without centralized planning . Self - organization can be seen in the global symmetry of certain crystals, for instance the apparent radial symmetry of snowflakes, which arises from purely local attractive and repulsive forces both between water molecules and between water molecules and their surrounding environment . </P> <P> Complex adaptive systems are special cases of complex systems that are adaptive in that they have the capacity to change and learn from experience . Examples of complex adaptive systems include the stock market, social insect and ant colonies, the biosphere and the ecosystem, the brain and the immune system, the cell and the developing embryo, manufacturing businesses and any human social group - based endeavor in a cultural and social system such as political parties or communities . </P> <P> Complex systems may have the following features: </P>

An example of a complex system in the u.s. is