REVIEW

the distances over which biological molecules and their complexes can function range from a few nanometres, in the case of folded structures, to millimetres, for example, during chromosome organization. Describing phenomena that cover such diverse length, and also time, scales requires models that capture the underlying physics for the particular length scale of interest. theoretical ideas, in particular, concepts from polymer physics, have guided the development of coarse-grained models to study folding of Dna, rna and proteins. more recently, such models and their variants have been applied to the functions of biological nanomachines. simulations using coarse-grained models are now poised to address a wide range of problems in biology. Minimal models that capture the essence of complex phenomena has a rich history in the natural sciences. In condensed matter physics, insights into many phenomena have emerged from analytic theories of models, which use effective many-body Hamiltonians that succinctly capture the essence of the problems1. Examples include phase transitions, superfluid-ity and superconductivity. However, complex problems, such as spin glasses2, structural glasses3,4 and a host of problems in biology like protein and RNA folding and functions of macromolecules, have resisted solutions using purely theoretical methods. These and other problems in material science, in which a wide range of time, energy, and length scales are intertwined, require well-designed com-puter simulations, which capture the essential features of the systems. Although the temptation t