Experiments on single NPs allow direct observation of NP-to-NP variations in kinetics, which are averaged out in ensemble measurements. It is important to note, however, that the NP and its surface structure are changed irreversibly by reactions; indeed, measuring the effects of nano-structural evolution on reactivity is one of the most interesting capabilities of the single NP mass spectrometry method. It does mean, however, that interpretation of measurements like those in Fig. , in which T NP or other reaction parameters are varied, is complicated by the fact that the NP also evolves over time under reaction conditions. For sublimation of NPs that were pre-heated above T melt prior to the kinetics measurement, the main effect is the decrease in surface area as the NP sublimes, which is accounted for in the area-normalized rate. More typically, however, sublimation also changes the distribution of NP surface sites, resulting in qualitative changes in kinetics in repeated T NP ramps. Chemical reactions tend to be especially sensitive to surface sites, and reactivity can change by orders of magnitude as reactions and annealing modify the surface structure. As a result, interpretation of experiments like that in Fig. , is complicated, and it is difficult to separate the effects of varying reaction conditions vs. evolving NP structure.