Before the invention of synthetically derived aroma molecules in the mid-1800s, vanillin being the first, perfumes were made with traditional extractions such as steam-distilled essential oils, tinctures, and enfleurages. The sources for these extractions were either botanical—flowers, leaves, twigs, buds, bark, resins, seeds, and roots—or animal such as ambergris (sperm whale sputum), castoreum (beaver gland), deer musk, civet (paste from anal gland), and hyraceum (fossilized urine).
Natural extractions are highly complex combinations of naturally occurring chemical constituents. A chemical analysis of a rose otto (steam distillation of rose petals) will reveal upward of 400 different and distinct naturally occurring chemicals that are present in various concentrations. Certain molecules such as geraniol, citronellol, or phenyl ethyl alcohol are present in higher concentrations and are responsible for the smell we recognize as "rose." But there are other components that help round out the scent. These ratios vary from flower to flower, season to season, and terroir, the location where the plant is cultivated. Soil conditions, water, sunlight, and climate conditions all contribute to the makeup of these chemicals and to their yield. Nature is a brilliant perfumer!
The rise of synthetically derived materials expanded the perfumer's palette. It also allowed perfumers to add constituents that would enhance or increase the concentration of a particular odor, rose, for example. Synthetic perfumery ingredients are individual molecules that are either found in nature (linalool, for example) and replicated from a non-botanical source or designed and created by a chemist (iso E super). A perfume made with synthetic ingredients often includes many notes blended into accords that build up a complex composition (some perfumes can have over 200 ingredients). By comparison, a natural perfume combines fewer ingredients that must be blended judiciously so as to maintain a clear structure that holds together during dry-down.