Sunshine-cured tobacco, Bastam, Iran Curing and subsequent getting older let for that gradual oxidation and degradation of carotenoids in tobacco leaf. This provides particular compounds inside the tobacco leaves and offers a sweet hay, tea, rose oil, or fruity aromatic flavor that contributes to your "smoothness" from the smoke. https://broadfar.com/non-combusted-cigarettes-a-safer-alternative-or-just-a-myth/