Experimental work on complex condensed matter can address a broad range of temporal and spatial scales, from femtosecond dynamics and atomistic detail to real-time macroscopic phenomena. Simulation methods in which each atom is explicitly represented are well established but have difficulty addressing many cooperative effects of experimental and theoretical interest. There is simply too large a gap between the time and spatial scales that govern typical intramolecular events and those which are relevant for collective motions. One example is the spatial rearrangement of membrane species such as occur in the formation of a lipid raft [1] or membrane fusion. Available simulation techniques for specific time and spatial scales are illustrated schematically in Fig. 2.1. These techniques take a variety of approaches to reduce the level of detail in the representation of the system under study as the time and/or length scales grow. This will be discussed further in Sect. 2.3. Bridging these disparate scales is possible with multiscale modeling [2,3,4] in which the various levels of treatment are coupled and fed back into one another.