These images illustrate optical microstructures resulting from a variety of deformation processes that are operative in the crust, ranging from localized faulting to distributed microcracking to pressure solution to dislocation creep to grain boundary sliding and diffusion creep, with and without accompanying phase changes. However most of the images illustrate microstructures produced by dislocation creep, because this is perhaps the dominant deformation mechanism in the mid to lower crust, and also has been well studied experimentally.