Ecological Systems Theory, also called "Development in Context" or "Human Ecology" theory, specifies four types of nested environmental systems, with bi-directional influences within and between the systems. The theory was developed by Urie Bronfenbrenner, generally regarded as one of the world's leading scholars in the field of developmental psychology. Later a fifth system was added:
* Microsystem: Immediate environments (family, school, peer group, neighborhood, and childcare environments)
* Mesosystem: A system comprised of connections between immediate environments (i.e., a child’s home and school)
* Exosystem: External environmental settings which only indirectly affect development (such as parent's workplace)
* Macrosystem: The larger cultural context (Eastern vs. Western culture, national economy, political culture, subculture)
* Chronosystem: The patterning of environmental events and transitions over the course of life.
The person's own biology may be considered part of the microsystem; thus the theory has recently sometimes been called "Bio-Ecological Systems Theory." Each system contains roles, norms, and rules that can powerfully shape development.