This chapter focuses on two fascinating neurodevelopmental disorders: autism and Williams syndrome. In autism, the discovery of low- and high functioning individuals with autistic spectrum disorder (ASD) among siblings and twins, and the discovery of variability in affectation among family members with the same gene, led to more acceptance of studying individuals without intellectual disability as a research strategy for gaining insight into the fundamental nature of the disorder. The hallmark strengths of autism were the remarkable memory for minute or inconsequential details and the often superior visuospatial abilities. In Williams syndrome, there is a severe visuospatial construction deficit resulting in an inability to construct a whole from parts. Puzzle assembly and block design are poor, but face and object identifications are normal. The potential contributions of neuroimaging research especially in combination with other modalities are on the brink of an entirely new world of discoveries.