The big difference between natural fragrance and artificial fragrance is complexity. Most artificial fragrance ingredients are made up of single molecules, whereas our natural ingredients are composed of up to 200 molecules each. As a result, the scope for intermolecular interaction is far greater with a natural fragrance.
Ffern fragrances, which are entirely made with natural ingredients, have a tendency to evolve over time. We think this is something to be embraced - and so we don't prescribe storage conditions for Ffern fragrance. That said, in general, the more light, temperature fluctuation and heat a fragrance is exposed to, the faster the rate of evolution.
So - if you're open to experimentation, then feel free to leave your bottle on the window sill (you'll likely see some colour changes too) - but if you're all about consistency, try to store it somewhere cool and dark, like our carry case!