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