Sunlight-cured tobacco, Bastam, Iran Curing and subsequent getting older allow to the slow oxidation and degradation of carotenoids in tobacco leaf. This generates particular compounds from the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic taste that contributes to the "smoothness" of the smoke. https://broadfar.com/oraco-global-trends-in-heat-not-burn-products/