Essential oils, commonly known as volatile oils, are aromatic oils extracted from plants, trees, or bushes. This involves a specific extraction method that uses a particular part of the plant. It can be its seeds, trees, roots, flowers and leaves. Keep in mind that these are stronger than dried herbs.
Always use therapeutic grade essential oil. It contains a complete ratio of chemical compounds, and preserves the natural coherent vibrational frequency of the plant it is obtained from. This is something you should pay more attention to, because it is the frequency, chemistry, and fragrance of the oil that determine its therapeutic effects.
You may know that carrots contain nutrients that protect your vision, but scientists have found that some essential oil have the same effect on vision and maintain eye health at optimal level.