This book provides professionals with the latest and most reliable information about genetic disorders and emphasises the advantage of a life-span multidisciplinary approach. The maturation of the brain, the environmental experiences and the mastery of developmental challenges and task are considered in order to understand how persons with genetic disorders and intellectual disability progress throughout their life-span from infancy to old age. The book utilises a developmental perspective and reviews different genetics disorders associated with intellectual disabilities (Down Syndrome, Nance Horan Syndrome, 10p deletion), with focus mainly at the developmental history. It also provides useful indications for support to children and adults with developmental disabilities regarding education and other best practices like family supports and cognitive enrichment programs. A Brief introduction to intelligence provides an overview of topical intelligence research and theory, in terms that can be integrated with the results and theory of neuropsychology. Case studies are proposed in each chapter to highlight specific diagnostic and treatment issues and to discuss the facilitation of transitions throughout the life-span from infancy to maturity and old age. Focusing developmental features for addressing the etiological diagnosis and comparing brain development and mind/brain interactions among neurogenetic syndromes is the promising approach to understand neurodevelopment underlined throughout the book.