What determines the composition of an essential oil? Why do so many essential oils contain the same constituents? Why are essential oils so complex? Do we use essential oils for the same reasons plants create their constituents? An “essential oil” is the liquid that is distilled (or expressed) from a plant. This class takes a dive into what happens before we harvest aromatic plants to create essential oils. Dr Ratajc looks at why and how plants create volatile compounds that form their essential oils, and explains what determines both the similarities and the variations in different oils.