Child maltreatment is a significant problem in North America. Maltreatment comes in many forms, such as neglect, physical abuse, sexual abuse, abandonment, and traumatic world events. The maltreatment affects children's neurobiological development, and thus, potentially their future quality of social and psychological health. This article gives a basic description of how the brain works and discusses the impact of trauma, particularly from birth to three years of age, on different aspects of the brain. It also contrasts the effects of trauma with the impact of nurture on the brain. The author demonstrates that what happens from birth to age three sets up the person's neuro-wiring for how individuals will respond to perceived traumatic events for the rest of their lives, and determines whether or not they will be prone to psychological disorders by the age of three or later on in life.