IN ESSENCE...
Rather than being synthetically manufactured in labs, essential oils are extracted from plant materials through removal methods that are suited to the specific plant part containing the oils.
Essential oils are the liquids that are isolated from plants when introduced to solvents – they are liquefied versions of the plants!
Popular extraction methods include: Steam Distillation, Solvent Extraction, CO2 Extraction, Maceration, Enfleurage, Cold Press Extraction, and Water Distillation.
The method of extraction affects essential oil quality by way of pressure and temperatures applied.
Some extraction methods are best suited to particular plant types and parts; for example, Cold Press extraction is better than Enfleurage for obtaining oils from citrus fruit peels, because the peels need to be pierced and squeezed, which is not achievable through Enfleurage.