Essential oils and essential oil plants have been used as medicine, aroma chemicals, preservatives, pheromones and attractants, cosmetics, coloring agent, in control of sanitary problems or as indicators of fresh water toxins produced by cyanobacteria etc. Essential oils are the complex mixture of isomers of hydrocarbons, mono- and sesqui-terpenes etc. In the current scenario separation of non- and semi-polar isomers is a big challenge. The work on aromatic plants present in this book was derived through extensive use of selective silver nitrate column chromatography, derivatization, inverted phase dry chromatography etc. along with the use of GC-MS, GC, HPLC, NMR for the identification, quantification and qualitative analysis of components. This book also deals with post harvest handling of some important industrial crops with the view of quality improvement and isolation of their major non volatile molecules (terpenoids, flavonoids etc). Most of the work present in this book is supported with their spectral evidences. The present work is an attempt to chemically explore some industrial crops and is useful for the workers in the research field of medicinal/aromatic plants.