This book examines basic knowledge in the field of infant and early childhood mental health. It focuses on cognitive, social, and emotional development of infants and toddlers and examines different aspects of neurobiological development, including genes and epigenetics as well as biobehavioral synchrony. In addition, the book addresses parenting and caregiving issues, including attachment, parent-infant relationships, and high-risk factors (e.g., the effects of trauma on the infant-caregiver relationship, adolescent parenting, and parents with substance abuse disorders). Key areas of coverage include: Social-emotional and cognitive development during infancy and early childhood. Temperament in infants and toddlers. Neurobiological influences from infancy through early childhood. Parenting and caregiving of infants and toddlers. Reflective functioning, mentalization, and infant development. The WAIMH Handbook of Infant and Early Childhood Mental Health, Volume One, is a must-have reference for researchers, professors, and graduate students as well as clinicians and all related therapists and professionals in infancy and early child development, developmental psychology, pediatrics, child and adolescent psychiatry, clinical social work, public health and all related disciplines.