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.
Urie Bronfenbrenner was generally regarded as one of the world's leading scholars in the field of developmental psychology. His ecological systems theory holds that development reflects the influence of several environmental systems, and it identifies five environmental systems that an individual interacts with.
- Microsystem: Refers to the institutions and groups that most immediately and directly impact the child's development including: family, school, religious institutions, neighborhood, and peers.
- Mesosystem: Refers to relations between microsystems or connections between contexts. Examples are the relation of family experiences to school experiences, school experiences to church experiences, and family experiences to peer experiences. For example, children whose parents have rejected them may have difficulty developing positive relations with teachers.
- Exosystem: Involves links between a social setting in which the individual does not have an active role and the individual's immediate context. For example, a husband's or child's experience at home may be influenced by a mother's experiences at work. The mother might receive a promotion that requires more travel, which might increase conflict with the husband and change patterns of interaction with the child.
- Macrosystem: Describes the culture in which individuals live. Cultural contexts include developing and industrialized countries, socioeconomic status, poverty, and ethnicity. A child, his or her parent, his or her school, and his or her parent's workplace are all part of a large cultural context. Members of a cultural group share a common identity, heritage, and values. The macrosystem evolves over time, because each successive generation may change the macrosystem, leading to their development in a unique macrosystem. 
- Chronosystem: The patterning of environmental events and transitions over the life course, as well as sociohistorical circumstances. For example, divorces are one transition. Researchers have found that the negative effects of divorce on children often peak in the first year after the divorce. By two years after the divorce, family interaction is less chaotic and more stable. As an example of sociohistorical circumstances, consider how the opportunities for women to pursue a career have increased during the last thirty years."
The person's own biology may be considered part of the microsystem; thus the theory has recently sometimes been called "Bio-Ecological Systems Theory."
Per this theoretical construction, each system contains roles, norms and rules which may shape psychological development. For example, an inner-city family faces many challenges which an affluent family in a gated community does not, and vice versa. The inner-city family is more likely to experience environmental hardships, like crime and squalor. On the other hand the sheltered family is more likely to lack the nurturing support of extended family.
Since its publication in 1979, Bronfenbrenner's major statement of this theory, The Ecology of Human Development  has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of his groundbreaking work in "human ecology", these environments — from the family to economic and political structures — have come to be viewed as part of the life course from childhood through adulthood.
Bronfenbrenner has identified Soviet developmental psychologist Lev Vygotsky and German-born psychologist Kurt Lewin as important influences on his theory.
Bronfenbrenner's work provides one of the foundational elements of the ecological counseling perspective, as espoused by Robert K. Conyne, Ellen Cook, and the University of Cincinnati Counseling Program.
There are many different theories related to human development. The ecological theory emphasizes environmental factors as playing the major role to development. .
- ^ Kail, R. V., & Cavanaugh, J. C. (2010). The Study of Human Development. Human Development: A Life-span View (5th ed.). Belmont, CA: Wadsworth Cengage Learning.
- ^ a b Santrock, John W. (2007). A Topical Approach to Life-Span Development. New York, NY: McGraw-Hill.
- ^ Vander Zanden, J. W., Crandell, T. L., Crandell, C. H. (2007).Human Development. 8th edition (ed.), New York: McGraw Hill.
- ^ Bronfenbrenner, U. (1979). The Ecology of Human Development: Experiments by Nature and Design. Cambridge, MA: Harvard University Press. (ISBN 0-674-22457-4)