Saffron is the dried red stigma of Crocus sativus, an autumn-flowering crocus, and by weight the most expensive spice in the world. Each lilac flower yields only three crimson threads, all picked and detached by hand, so that it takes on the order of 150 flowers to make a single gram. Steeped in warm liquid the threads bleed a vivid golden-orange and release a haunting aroma — sweet, hay-like and honeyed, with a dried-grass, faintly metallic, almost medicinal edge — over a distinctive bitter undertaste. It is the soul of Spanish paella, Persian and Indian rice, Milanese risotto, French bouillabaisse and a hundred celebratory dishes from Morocco to Sweden.