This symposium will focus on the dynamic behavior, structure, and performance of structural and functional materials in response to coupled extreme environments. Focus will be restricted to these coupled environments where two or more environmental factors are present, including but not limited to extreme temperatures, cyclic fatigue, radiation exposure, corrosive environments, high pressures, or high magnetic fields. Driving materials with such environmental factors often produces unique dynamic changes in structures and properties which are otherwise impossible to achieve, for example the generation of gas bubble superlattices in metals exposed to high temperatures, gas loading, and irradiation. A connection between materials physics and engineering systems of interest will be encouraged as many systems such as future fusion power plants, high efficiency turbines, and satellites may involve these environmental conditions. One portion of the symposium will particularly focus on emerging in situ experimentation capable of providing time-resolved performance and structure insight into these dynamic and/or transient processes. Besides novel in situ instruments and observations, innovative approaches and algorithms developed to synchronize, track, and classify in situ data and to generate high throughput analysis are encouraged to push boundaries for quantitative understanding of materials dynamics and transformations. A second portion of the symposium will focus on modeling and simulation of materials under these coupled extremes across multiple length scales, from the atomic resolution calculation of defect generation to time-accelerated dynamics of degradation over complete system lifetimes. A final, linking component will specifically target modeling and simulation that attempts to connect directly to in situ experimental modalities either as a tool for the design and implementation of experiments or as a pathway to understand in detail measured properties and structures.