Essential oils are volatile aroma compounds extracted from plants. They are liquid, oily and highly concentrated products. Essential oils are extracted from different parts of the aromatic plants (leaves, flowers, bark, rind of the fruit, etc.), through distillation or mechanical processes (cold pressing). They can be used for internal use, on the skin (through massages for example), or by air diffusion (for example by steaming the oil in the environment with an air diffuser).