PREPARING AND PRESENTING CONTENT

Systems and techniques to prepare and present content. In general, in one implementation, a technique includes receiving information identifying a first streaming content element describing a first scope of material, receiving information identifying a second streaming content element describing a second scope of material, and describing a presentation including the first streaming content element and the second streaming content element in a parent/child relationship. The second scope of material can be more detailed than the first scope and included in the first scope.