"The proposed book will present chemical characterization of essential oils and various uses, which will enrich chemical knowledge of useful plants. Specifically, characterization of useful medicinal species will be shown compared with species of the same family. In some cases the essential oils of a species in different types of habitat will be compared showing knowledge of the most useful ecosystems, plant taxa, categories of use and indigenous groups. The book will identify not only essential oils but also the uses of the majority oils in different drug systems, and related factors that affect it. Recent research will show that essential oils play an important role in the use of medicinal plants and relationships with their traditional use will be established. Researchers from several continents will demonstrate the importance of essential oils, that regardless of the geographical region, the social, medical and / or traditional role of the studied species can be demonstrated"--