Sun-cured tobacco, Bastam, Iran Curing and subsequent getting old let for that gradual oxidation and degradation of carotenoids in tobacco leaf. This produces particular compounds during the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic taste that contributes for the "smoothness" of your smoke. https://broadfar.com/nuso-heated-tobacco-smarter-alternative-to-traditional-smoking/