  Every electron crystallography experiment is fundamentally limited by
radiation damage. Nevertheless, little is known about the onset and progression
of radiolysis in beam-sensitive molecular crystals. Here we apply
ambient-temperature scanning nanobeam electron diffraction to record
simultaneous dual-space snapshots of organic and organometallic nanocrystals at
sequential stages of beam-induced radiolytic decay. We show that the underlying
mosaic of coherently diffracting zones (CDZs) continuously undergoes spatial
reorientation as a function of accumulating electron exposure, causing the
intensities of many Bragg reflections to fade nonmonotonically. Furthermore, we
demonstrate that repeated irradiation at a single probe position leads to the
concentric propagation of delocalized radiolytic damage well beyond the initial
point of impact. These results sharpen our understanding of molecular crystals
as conglomerates of CDZs whose complex lattice structure deteriorates through a
series of dynamic internal changes during exposure to ionizing radiation.
