However, due to the limited spatial resolution of the low dose in situ STEM imaging required to prevent electron beam damage, it is not possible at this time to distinguish whether the dissolutionrecrystallization or surface diffusion mechanism control the curvature fluctuation dynamics. with each dissolution step occurring along a single <100> plane, as opposed to dissolving continuously and isotropically along all crystal directions. This is exemplified in the images at the 296 s and 302 s time points and shown by the time dependent NaCl projected area (Figure ) and time dependent droplet growth and particle dissolution rates (Figure ). The dissolution rate plot in Figure shows that discrete dissolution steps were interspersed by lag times of several seconds where the particle area remained constant. The liquid droplet surrounding the NaCl displayed discrete growth steps that mirrored the particle dissolution steps in time. Correlation analysis of the droplet growth and NaCl dissolution rates showed strong anti-correlation with a Pearson's correlation coefficient of R = -0.84. The terrace-ledge-framework for crystal dissolution predicts that dissolution begins from a defect site at the corner of the NaCl, which then propagates across the crystal face to remove the entire crystal plane. Our observations show that this mechanism can rapidly remove several lattice planes in a few seconds. ⁄ 𝜌 𝑁𝑎𝐶𝑙 (Figure ). The mass normalized dissolution rate ranged from 10 -3 -10 -1 s -1 and increased as a function of time and RH, in agreement with the prior measurements by Ma et al. for micron sized NaCl aerosol particles. However, in contrast to the prior work, the in situ observations here showed that the instantaneous dissolution rate did not increase monotonically with increasing RH due to the intermittent dissolution process. Instead, this analysis revealed that the average dissolution rate increased with RH due to more frequent and larger dissolution steps. As the RH increased the water condensation rate onto the surface of the droplet increased, decreasing the droplet solute concentration and thus increasing the thermodynamic driving force for crystal defect generation and crystal plane dissolution. Taking the ensemble average over many particles undergoing this discrete dissolution process would indeed be expected to produce an apparent monotonic increase in dissolution rate as observed by Ma et al.