The first separations of essential oil were carried out on packed columns that provide limited efficiency but, nevertheless represented a tremendous advance on distillation. The introduction of the technique of temperature programming improved the separation even more. However, it was not until the capillary column, with its many thousands of theoretical plates, became commercially available that the true complex nature of many of the essential oils was revealed. The chemical structure of the individual components of many of the oils, elucidated by the GC/MS tandem systems, provided the knowledge necessary to synthesize a number of commercially important synthetic flavors. For synthetic example, the synthetic flavors that closely imitate those of the peach, melon and other fruits that are presently available to the contemporary food chemist are a direct result of the separating capabilities of gas chromatography.