Nader Engheta - University of Pennsylvania Metamaterials and metasurfaces have provided unprecedented possibilities in achieving “extremes” in wave-matter interaction. Numerous exciting functionalities have been achieved in exploiting these platforms in nanophotonics and nano-optics. We have been exploring how 4D metamaterials, i.e., spatiotemporal materials in which the material parameters may change with time instead of (or in addition to) spatial inhomogeneities of material parameters, can lead to new opportunities for exploiting waves for certain useful functions. In my group, we are investigating several scenarios of such metastructures. As one scenario, we have been developing metastructure platforms that can perform analog computation such as solving integral and differential equations and inverting matrices with waves as waves interact with them. These “metamaterial machines” can function as wave-based analog computing structures, suitable for micro- and nanoscale integration. Another scenario deals with 4-dimensional metamaterials and their wave features such as “freezing and growing waves” in combination with the non-Foster circuits, anti-reflection temporal coating, and temporal anisotropy, just to name a few. In this talk, I will give an overview of some of our ongoing efforts in this area.