The fragrance of ﬂowers derives from volatile oils known as essential oils. More than three thousand essential oils have been identiﬁed from over eight-seven plant families worldwide. These oils are not found only in the ﬂowers, but also frequently in the leaves, roots, rhizomes, seeds, rind, or bark. Plants usually produce these oils as a defense against insect attack, plant diseases, or extreme heat. The bioactivity of essential oils is the key to their potency as plant defenses and to their therapeutic properties. White ﬂowers are disproportionately represented in scented genera, because the oilproducing glands compete for location with cells producing pigmentation.