Plant essential oils have been used for centuries in the preparation of cosmetic fragrances and food flavours, as well as in traditional medicines as therapeutic remedies. In recent years they have been attracting the renewed interest of both the scientific community and the general public. Their use in different aspects of human life is generally regarded as being part of a healthier, natural-oriented life style. On the other hand, a wealth of scientific studies has been documenting their biological properties, particularly associated with their antimicrobial and antioxidant activities, although additional medicinal properties have also been brought to light. This book offers an up-to-date examination of scientific literature on the antimicrobial and antioxidant activity of main dietary essential oils from all over the world, together with a general introduction to their chemistry, classification, bio-synthetic origin, preparation and analysis.