Sun-cured tobacco, Bastam, Iran Curing and subsequent aging allow for with the gradual oxidation and degradation of carotenoids in tobacco leaf. This produces certain compounds in the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes for the "smoothness" from the smoke. https://broadfar.com/the-benefits-of-switching-to-nusos-heated-tobacco-solutions/