Afundamental challenge in materials science today is the investigation of size effects that influence the mechanical properties of micrometer-to nanometerscale devices. These small scales are ubiquitous in modern technological applications and pose new theoretical questions as a result of the crucial role played by fluctuations. These fluctuations are observed as step changes or discontinuities in the mechanical response caused by the inhomogeneous dynamics of defects at the microscale. Fluctuations of this kind become more important as the size of any physical system decreases, hence they can lead to substantial deviations from the system’s average behavior. On page 1188 of this issue, Dimiduk and co-workers (1) report experimental results on metal microcrystals that provide direct evidence of scale-invariant intermittent plastic flow—that is, permanent deformation with strain bursts that have a power-law distribution. These high-resolution experiments call for a novel theoretical framework that could help unravel microscopic deformation behavior in crystalline materials. Plastic deformation is often described as a smooth process occurring in an elastic continuum. Yet microscopically it is due to the nucleation and motion of discrete crystal defects, known as dislocations. Dislocations self-assemble into intricate structures that determine the mechanical properties of a crystalline material. When external forces are applied, these dislocation structures dis-