However, for crystals of certain compounds, a second sweep sometimes granted improved data reduction statistics. This was true of certain biotin and Zn(II)-methionine crystals diffracted at 100 K (Supplementary Tables and), and certain Zn(II)-histidine crystals diffracted at room temperature (Supplementary Table ), using our lowest dose rate of 0.01 e -/Å 2 s. Of the four Zn(II)-methionine crystals we interrogated under these conditions, half displayed this behavior. We rationalize these observations by noting that Zn(II)-methionine undergoes substantial beaminduced reorientations at 100K during the first 1 e -/Å 2 of exposure, and that a second sweep may enable capture of a period less impacted by reorientations while still evading the onset of the most deleterious effects of beam-induced decay. In most biotin crystals at 100 K, which exhibit reorientations less dramatic than Zn(II)-methionine, data reduction statistics worsen monotonically over successive sweeps. We surmise, then, that reorientations in biotin crystals at 100 K are most often sufficiently mild that any advantage gained from acquiring data after they occur most distinctly is outweighed by the detrimental impact of global decay on data reduction statistics. This indicates a tradeoff between the effects of beam-induced reorientation and decay that occur as a given crystal accumulates electron beam fluence, which can be optimized for crystals of a given compound.