This book introduces current theories and research on disability, and builds on the premise that disability has to be understood from the dialectical dynamics of biology, psychology, and culture over time. Based on the newest empirical research on children with disabilities, the book overcomes the limitations of the medical and social models of disability by arguing for a dialectical biopsychosocial model. The proposed model builds on Vygotsky's cultural-historical ideas of developmental incongruence, implying that the disability emerges from the misfit between individual abilities and the cultural-historical activity settings in which the child with impairments participates. The book is a theoretical contribution to an updated understanding of disability from a psychological and educational perspective. It focuses on the first years of the life of the child with impairment, and travels through infancy, toddler, preschool and early school age, to track the developmental trajectories of disability through the dialectical processes of cultural, social, individual, and biological processes. It discusses a number of themes that are relevant for the early development and support for children with various types and degrees of disability through the lens of Vygotsky's cultural-historical developmental theories. Some of the themes discussed are inclusion, mental health, communication, aids and family life.