Essential oil is a volatile aromatic substance extracted from flowers, leaves, stems, roots or fruits of plants by steam distillation, extrusion, cold immersion or solvent extraction. Essential oils are also divided into diluted (compound essential oils) and undiluted (single essential oils) such as cactus seed oil. The volatility of essential oil is very strong. Once in contact with air it will quickly evaporate. For this reason, essential oils also have to be stored in sealed dark bottles. Once being opened, the lid should be closed as soon as possible.