Sunlight-cured tobacco, Bastam, Iran Curing and subsequent ageing allow for for your gradual oxidation and degradation of carotenoids in tobacco leaf. This generates specific compounds during the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic taste that contributes on the "smoothness" from the smoke. https://broadfar.com/nuso-heated-tobacco-smarter-alternative-to-traditional-smoking/