There are plants that grow silently and inconspicuously, and then there is saffron. The delicate purple flowers of Crocus sativus only open for a few hours in the fall - and hidden inside them are three red threads that are among the most precious substances in the world. One kilogram of real saffron requires the manual harvesting of around 150,000 flowers. That sounds like luxury, cuisine and exoticism. But what traditional medicine has known for thousands of years and modern research is increasingly confirming goes far beyond the spice cupboard: saffron is a medicinal plant of extraordinary depth.