In this introductory chapter, guided by developmental psychopathology and developmental science as overarching integrative theoretical frameworks, the authors define three constructs related to social anxiety in childhood (behavioral inhibition, anxious solitude/withdrawal, and social anxiety disorder) and analyze commonalities and differences in the content and assessment of these constructs. They then highlight controversies between developmental and clinical approaches to the definition of these constructs, the role of biology in social anxiety, age of onset of social anxiety, information processing biases in social anxiety, heterogeneity in the social and emotional adjustment of socially anxious children, and targets of intervention for childhood social anxiety.