Many important materials science applications (e.g. microelectronic devices, optics, solar cells, and semiconductor lasers) depend, for their functionality, on electronic excited-state properties of materials. Likewise, most experimental probes create excitations and consequent materials' response. Modern photon sources (synchrotrons, ultra-fast lasers, etc.) now probe materials with unprecedented resolution and offer the potential for novel materials studies. In recent decades, computational physics has achieved enormous successes in describing ground-state properties; however, quantitative and reliable descriptions of excitations and response functions are just emerging. The objective of the proposed cooperative research team (CRT) is to attack these challenging, but timely, scientific and computational issues. The proposal has specific short- and long-term objectives, aimed at creating a deeper theoretical understanding through predictive calculations of materials' properties involving excited states. Our effort naturally breaks into three interconnected parts, a) experimental processes and applications; b) fundamental electronic excitations and correlations; and c) time-dependent phenomena and non-linear effects. We plan to develop compatible computational tools that can be shared between groups in a way that fosters parallel, interrelated, and compatible efforts.