*2.3.1.1.1 Hydrodistillation*

It is the oldest and easiest conventional method of extraction of EOs [11, 29–31]. The principle is based on the isotropic distillation. The plant material soaks up water during the boiling process, and the oil contained in the oil cells diffuses through the cell walls by means of osmosis. The distillation time depends on the plants material being processed (**Figure 1**).
