The fragrant substances used in perfumery are extracted thanks to several processes depending on their concentration in the plant, their fragility (in particular their sensitivity to heat), and the cost constraints. Steam distillation (hydrodistillation), which produces essential oils, is the most frequently used. The longer, more complex, and, therefore, more expensive enfleurage and maceration methods provide the absolutes. Finally, the simple pressure extraction of the citrus zest makes it possible to obtain essences.