Neuroimaging studies of children, whether cross-sectional or longitudinal, are developmental in nature. This aspect requires the careful consideration and evaluation of maturational changes over time. In addition, the basis for understanding aberrant brain development rests with an understanding of normal maturation. Consequently, this section outlines brain and cognitive development and critically discusses the use of cognitive and behavioral probes in developmental imaging studies. Casanova and his colleagues provide a thoughtful and thorough review of brain development from the level of the cell to the level of gross functional anatomy and discuss the impact of genes and environment on brain organization and its evolution (Chapter 7). Pascualvaca and Morote provide an overview of the developmental trajectories of specific cognitive and neuropsychological functions (Chapter 8). Casey and her colleagues address the important themes of ageappropriate tasks for use in functional neuroimaging studies of children, illustrating these themes with paradigms used to explore prefrontal cortical functioning (Chapter 9). Together, these chapters provide an overview of brain development and cognitive development and illustrate how the two come together in study designs appropriate for mapping human brain functional development.