A central question in developmental science, and particularly in the study of developmental psychopathology, is how and when developmental trajectories are most vulnerable to delay or deviance, leading to greater risk for later-life psychopathology. There has been increasing focus on early childhood as a foundational period setting the stage for later adaptive or maladaptive social and emotional development key to well-being or psychopathology. At the same time, there has been renewed interest-empirical support in animal models, as well as some in human subjects-in the notion that early-life experiences and exposures are uniquely influential to long-term outcomes due to heightened neuroplasticity during early childhood sensitive periods (1). Illustrative of this process are the significant breakthroughs in our understanding of the development of attachment with the operationalization of paradigms to study attachment in toddlers using the Strange Situation assessment. This observational assessment utilizing a mild and increasing series of stressors (separations from caretakers), during which child behavior was systematically coded, represents an innovation in methodology now more broadly used to tap a variety of emotional and behavioral constructs in early childhood. Studies utilizing the Strange Situation paradigm provided critical empirical data to inform the development of attachment systems and the parenting behaviors associated with secure or insecure attachment, building on theories articulated by John Bowlby. A large body of literature has now established the parameters of secure attachment relationships and their predictive validity (2). There is also support for a sensitive period in early childhood when access to a nurturing and consistent caregiver has proven critical for this process to proceed in a healthy fashion (3). With this as a framework, the Attachment and Biobehavioral Catch-Up (ABC) early intervention was designed and tested in randomized controlled trials showing significant effects for later positive behavioral outcomes, including secure attachment (4).