Many theorists now believe that development emerges out of the coming together of multiple influences on the developing organism. To understand development, not only is it important to identify these influences, but it is necessary to describe their relationship to one another. In this dynamic view of development, emergent organization is the result of the components of development coming together. Timing is concerned with the relationship between components that have different rates of development. This book brings together the work of several investigators who have contributed to our understanding of the impact of timing on development through the examination of different functions and different organisms. By juxtaposing their work it is possible to see that the concept of timing has explanatory value at various levels of organization for the understanding of development. The book's unifying theme allows the reader to make conceptual analogies across species and across levels of organization without being reductionistic. Presenting the work of researchers in developmental and experimental psychology, biopsychology, neuropsychology, life span development, and medicine, the book offers a theoretical base from which to examine the value of using timing as a construct and specific examples of research programs which have utilized timing to frame their research questions.