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