This chapter provides a background to the world of natural products chemistry for non-specialists. Knowing how the chemistry used by plants produces the substances responsible for eliciting the perception of odour helps one to appreciate the variety of natural chemicals made by plants and how they relate to scent. Investigating the roles that odorous natural products play in the plants that produce them raises some interesting questions about Biblical perfumery and some key differences between that and modern perfumery. Before describing each Biblical perfume ingredient in detail, it is worth considering how and why they are made in nature, where they came from, how they were extracted and how they were stored.