Developmental psychology
Attachment theory, originally developed by John Bowlby, focuses on the importance of open, intimate, emotionally meaningful relationships. Attachment is described as a biological system or powerful survival impulse that evolved to ensure the survival of the infant. A child who is threatened or stressed will move toward caregivers who create a sense of physical, emotional and psychological safety for the individual. Attachment feeds on body contact and familiarity. Later Mary Ainsworth developed the Strange Situation protocol and the concept of the secure base.
Marc David Lewis
Through a sabbatical at the University of Oregon in 2000-2001, Lewis took the next step in developing his integrated model by delving into the neural underpinnings of emotion regulation. His current research program tests this model by examining brain and behavior in normal and clinically referred children and assessing neural changes corresponding with successful treatment. His papers on the contribution of dynamic systems theory and affective neuroscience to understanding human development and clinical syndromes have appeared in journals such as "Child Development", "Behavioral and Brain Sciences", "Development and Psychopathology", and "Perspectives on Psychological Science". He has also co-authored two books with his wife, Dr. Isabela Granic. The first is an edited volume of dynamic systems approaches to emotional development. The second is a guide for parents about when to attempt sleep training with toddlers. 
Dr. Lewis' most recent book, "Memoirs of an Addicted Brain", is an account of his addiction to drugs as a young man with accompanying explanations of the neurobiological processes underlying various drug experiences as well as the process of addiction itself.