Terpenes are the most diverse and largest family of secondary metabolites in Nature, in which they involve in various duties from primary to secondary and less important ones. Learning about them, especially their regulation and expression in organisms particularly plants will be of crucial value. Why Plants, because they are the basis in most food chains on this planet. In this piece of work, their importance in plant at first and then difficulties and successes with their biotechnologically manipulation will be reviewed. I hope, this work will be useful for those who want to get a generic gist of the importance of terpenes in plants, and to know about problems around their genetic manipulations, and still to be glad about some successes in this field. In the end, this work is just a little introduction to start.