Ground-breaking progress in the field of neurodevelopmental disorders has allowed us far more insight into blindness and visual impairment (VI). The field of cognitive neuroscience has now established itself solidly in the literature, combining the knowledge from cognitive psychology, clinical studies related to brain damage, and neuroscience to open the way to significant advances in understanding. In recent years, the optimism engendered from the adult studies has played a large part in providing the impetus for developmental studies and in particular developmental neuroscience (Johnson 2005; Tager-Flusberg 1999). It is from this developmental neuroscience perspective that we can begin to understand the cognitive and behavioral manifestations associated with blindness and VI; albeit with the proviso that children with VI present particularly heterogeneous developmental patterns when compared to typically developing children (Fraiberg 1971). In considering the effects of blindness and VI, this chapter will focus on social understanding, language, cognition, and motor development. However, it begins with brief introductions to epidemiology and the effects of blindness on the functional and structural organization of the brain, which it is hoped will provide a useful context in which to consider the development of children who cannot see. Today the number of blind people in the world stands at 45 million, even though up to 75% of blindness could be avoided either by treatment or by prevention. The number of people with avoidable blindness will have doubled from 1990 to 2020 unless there is rapid and effective intervention, and the total number of the blind is projected to be as many as 76 million by 2020. To prevent this scenario, the World Health Organization (WHO) and the International Agency for the Prevention of Blindness (IAPB) have jointly initiated Vision 2020, a project that aims to eliminate the main causes of avoidable blindness by the year 2020, with the ultimate long-term goal of a world in which all avoidable blindness is eliminated and in which everyone with unavoidable vision loss reaches their full potential. The top priority of Vision 2020 is the prevention of childhood blindness. At present there are 1.4 million children under the age of 15 who are blind.