Terpenes constitute a huge and important class of natural products. A wide range of active compounds—from anticancer compounds to perfumes, cosmetics, foods, and hormones—terpenes are commonly found in every aspect of modern life. In spices and incenses, the very first terpenoids described were part of the cooking procedures and religious curative rituals in the thirteenth century. Since that time, and increasingly nowadays, light terpenoids from aromatic plants perfume our life and heavy terpenes such as Taxol® and ginkgolides are used to treat and cure as never before. The origin of the term terpene, one of the first resinous substances characterized, the historical aspects, and a glimpse of the use and the semi-synthesis processes of these important natural products are presented in this chapter.