However, previous studies indirectly observed similar behavior. Specifically, Liang et al. (2021) observed the formation of inclusions/bubbles within supermicron particles containing ammonium nitrate and sucrose exposed to UV light. Liang et al. suggested the formation of inclusions/bubbles could be due to: 1) the fast production rate of NO2 and NO by photolysis of ammonium nitrate; 2) the slow loss rate of NO2 and NO by molecular diffusion to the surface of the particles followed by evaporation. These arguments are very similar to the explanations presented in this work. In general, we expect that inclusions/bubbles are expected in supermicron particles during heating or photolysis if there is fast production of high volatility compounds (e.g., NO2, acetone, CO, CO2) and high material viscosities, which limits the loss rate of these high volatility compounds.