The occurrence of beam-induced reorientations in crystals at both room and cryogenic temperatures suggests the phenomenon is not induced by temperature or vitrification, or an artifact of interrogating specimens arrested in vitreous ice. This further challenges the notion that crystal reorientation in MicroED experiments results from a beam-induced crinkling effect on the sample support film, which is expected to be accentuated in cryogenic experiments . Instead, our results support the well-known protective effect of cryogenic temperatures on slowing of radiolytic damage-induced intensity decay in electron diffraction, and further link lattice reorientations to beam-induced damage. In contrast, vitrification in an aqueous matrix had little effect on lattice reorientation. For example, AVAAGA peptide crystals behaved similarly at 100 K whether or not they were vitrified. While we observed no reorientation in proteinase K crystals, it is possible that given the greater complexity of a protein crystal lattice compared to those of smaller molecules, reorientations may not be coherent and may not manifest as measurable changes in overall lattice orientation. Instead, such motions might globally decrease the degree of order within a protein crystal, limiting excitation of higher-resolution reflections. As an alternative hypothesis, reorientations in proteinase K crystals might have occurred during our experiments, but at extremely low doses, and been largely completed by the time we were able to acquire more than a frame of data, allowing them to be missed by our analysis (Fig. ).