"Why study structure in biology? The imaging of structure has long been of interest, where structures range in length scale from an entire ecosystem to the gross anatomy of the human body, to cellular, molecular, and atomic structure. Here, we concentrate on structure at the molecular and atomic level and on the essential, dynamic variations in structure with time. Determining biological structure at this level is undeniably powerful, as evidenced by the library of more than 160,000 experimental and increasingly, computational structures in the Protein Data Bank (PDB). An arguably more interesting reason is broader: structure at the molecular and atomic level provides a powerful avenue into understanding both function and mechanism."-- Provided by publisher.