This book highlights the advances in essential oil research, from the plant physiology perspective to large-scale production, including bioanalytical methods and industrial applications. The book is divided into 4 sections. The first one is focused on essential oil composition and why plants produce these compounds that have been used by humans since ancient times. Part 2 presents an update on the use of essential oils in various areas, including food and pharma industries as well as agriculture. In part 3 readers will find new trends in bioanalytical methods. Lastly, part 4 presents a number of approaches to increase essential oil production, such as in vitro and hairy root culture, metabolic engineering and biotechnology. Altogether, this volume offers a comprehensive look at what researchers have been doing over the last years to better understand these compounds and how to explore them for the benefit of the society.