Spices contain volatile organic substances, often called aromas. These organic substances belong to chemical groups such as alcohols or aldehydes and stimulate olfactory and gustatory perceptions. They are therefore responsible for odours, aromas and flavours and are used in small quantities in cooking as a preservative, seasoning or colouring. Spices are to be distinguished from other products used to flavour dishes, such as herbs or fruits.

They are mostly exotic products, which explains why spices were among the most expensive commercial products in antiquity and the Middle Ages. Many spices were used in medicine in the past. The most expensive spice is saffron, followed by vanilla and cardamom.

In Morocco a stroll through the spice souks is an unforgettable experience.