The iris is considered one of the most precious ingredients among perfumeries and it has been used by the industry for hundreds of years. Although there are more than 300 species, only three are thought to be used in fragrances. It is one of the most expensive ingredients used by the industry - 2kg of essential oil is extracted from every tonne of iris. The oils from the rhizomes produce a thick compound called iris butter, which contains many fragrances used in the industry. Infusion d'Iris (HK$545, right) is a new scent from Prada built around the flower's extract. Orange blossom and incense, and the earthy, woody aromas of galbanum and lentisc, vetiver and cedarwood are combined to create what the brand describes as a light, fresh sensual scent.