Dynamically arrested states of matter

We outline current developments in our understanding of dynamical arrest, that phenomenon in which many particles stop moving in a collective manner. However in addition to the question of true dynamical arrest itself, we emphasize the development of new tools that can describe relatively sharp changes in the way that ergodic systems may be explored. We discuss the concept of new order parameters (dynamically available volume), and indicate how they may be applied to understand dramatic slowing phenomena present in particle systems, and other arenas of soft and complex matter.