This book reports the work of a 20-year collaboration between a multidisciplinary group of clinicians and developmental scientists who have created and investigated a new tool to elicit and analyze children's narratives. This tool is the MacArthur Story Stem Battery, a systematic collection of story beginnings that are referred to as 'stems.' These stems are designed to elicit information from children about their representational worlds. This method is particularly exciting because using it allows developmental psychologists and others to gain information directly from children about their emotional states and what they are able to understand, and in turn, to use this information to explore significant emotional differences among children. This work will appeal to researchers and practitioners in developmental and clinical psychology.