Sunshine-cured tobacco, Bastam, Iran Curing and subsequent ageing allow for with the sluggish oxidation and degradation of carotenoids in tobacco leaf. This creates particular compounds within the tobacco leaves and gives a sweet hay, tea, rose oil, or fruity aromatic taste that contributes to your "smoothness" on the smoke. https://broadfar.com/non-combusted-cigarettes-a-safer-alternative-or-just-a-myth/