Nonlinear Dynamic Systems Theory is discussed by three child, adolescent, and adult analysts who use this theory in their thinking about development from infancy through old age and as a way of understanding the process of change in psychoanalysis. This theory explains how the systems of the brain, the body, the environment, and the culture interact and help determine character formation throughout the life cycle. Examples of development and psychoanalytic treatment are used to demonstrate the application of nonlinear dynamic systems.