Sun-cured tobacco, Bastam, Iran Curing and subsequent ageing make it possible for with the slow oxidation and degradation of carotenoids in tobacco leaf. This creates specific compounds while in the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic taste that contributes to the "smoothness" https://broadfar.com/nuso-heated-tobacco-smarter-alternative-to-traditional-smoking/