Time is inherent to biological processes. It determines the order of events and the speed at which they take place. This is particularly obvious during embryonic development where the sequence and rate of events ensures that structures develop in the right place, at the right time. Modifying the developmental tempo can affect the final size and composition of tissues, as well as their plasticity and function. Strikingly, comparisons between species reveals that, although the order and underlying molecular mechanisms are often indistinguishable, the pace at which they advance can differ substantially. Hence comparison of biological processes between species is likely to provide insight into time-keeping mechanisms and how they change. Despite the centrality of these questions to embryo development, and evolution, it has remained an understudied topic. This conference will foster dialogue between researchers from different fields to stimulate new ideas and catalyse the study of the genetic, molecular and cellular mechanisms controlling the tempo of embryonic development.