Sunshine-cured tobacco, Bastam, Iran Curing and subsequent ageing allow for to the gradual oxidation and degradation of carotenoids in tobacco leaf. This creates particular compounds within the tobacco leaves and provides a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes to the "smoothness" of the smoke. https://broadfar.com/heated-tobacco-shaping-a-safer-sustainable-smoking-future/