If the structure of spacetime is different than that readily observed, gravitational physics, and cosmology are all immediately affected. the physics of extra dimensions offers new insights and solutions to fundamental questions arising in these fields. Novel ideas and frameworks are continuously born and evolved. They make use of string theoretical features and tools and they may reveal if and how the 11-dimensional string theory is relevant to our four-dimensional world. We have outlined some of the experimental observations in particle and gravitational physics as well as astrophysical and cosmological considerations that can constrain or confirm these scenarios. These developing ideas and the wide inter-disciplinary expe- rimental program that is charted out to investigate them mark a renewed effort to describe the dynamics behind spacetime. We look forward to the dicovery of a higher dimensional spacetime!