Plant volatiles (PVs) are lipophilic molecules with high vapor pressure that play important ecological roles. Their biosynthesis involves various reactions, including the removal of hydrophilic groups and oxidation, reduction, methylation, and acylation. PV biosynthetic enzymes can produce multiple products from a single substrate or act on multiple substrates. Genes for PV biosynthesis evolve through gene duplication and divergence, leading to specialized metabolites. Convergent evolution allows distantly related species to synthesize the same volatile. PVs are typically lipophilic liquids with high vapor pressure. Nonconjugated PVs can cross membranes freely and evaporate into the atmosphere. Over 1000 volatile chemicals have been identified from various plants, with more likely to be discovered. PVs serve multiple functions in floral and vegetative organs, often not related to their volatility. Most PVs are restricted to specific lineages and are involved in species-specific ecological interactions. PVs are important for pollinator attraction and have applications in flavoring, preservation, and herbal remedies. Flower and herb aromas may contain many individual chemicals, with little overlap in PV profiles between closely related species. The diversity of PVs suggests frequent changes in enzymatic profiles through evolution. Nonvolatile specialized metabolites also show diversity and rapid change, raising similar questions about evolutionary mechanisms. Advances in analytical techniques have made PVs one of the best-studied groups of plant secondary metabolites. The biosynthesis of PVs involves pathways derived from isoprenoid metabolism, including terpene synthases (TPSs) that produce diverse PVs. TPSs catalyze the formation of hemi-, mono-, sesqui-, and diterpene PVs from various precursors. TPSs have multiple functional variants, with some producing multiple products. PVs can also be derived from aromatic rings, phenylalanine derivatives, and type III polyketide synthases. Oxidative cleavage and decarboxylation of fatty acids produce shorter-chain volatiles. Some PVs are produced by cleavage of carotenoids or modified amino acids. Enzymes for PV biosynthesis often belong to large families, with some evolving from non-PV enzymes. Some modifying enzymes can use multiple substrates, and gene duplication and divergence contribute to functional divergence. Enzymes for PV biosynthesis often evolve from non-PV enzymes, with some P450 oxidases involved in PV biosynthesis. The spatial and temporal regulation of PV biosynthesis occurs in specific cells and tissues, with biosynthesis rates correlated with gene expression and substrate availability. Environmental factors such as light, temperature, and moisture influence PV biosynthesis, often following a rhythmic pattern. The transport, storage, and emission of PVs are areas requiring further study. Overall, PVs are diverse and play important roles in plant ecology and human applications. Many PVs and their biosynthetic enzymes remain toPlant volatiles (PVs) are lipophilic molecules with high vapor pressure that play important ecological roles. Their biosynthesis involves various reactions, including the removal of hydrophilic groups and oxidation, reduction, methylation, and acylation. PV biosynthetic enzymes can produce multiple products from a single substrate or act on multiple substrates. Genes for PV biosynthesis evolve through gene duplication and divergence, leading to specialized metabolites. Convergent evolution allows distantly related species to synthesize the same volatile. PVs are typically lipophilic liquids with high vapor pressure. Nonconjugated PVs can cross membranes freely and evaporate into the atmosphere. Over 1000 volatile chemicals have been identified from various plants, with more likely to be discovered. PVs serve multiple functions in floral and vegetative organs, often not related to their volatility. Most PVs are restricted to specific lineages and are involved in species-specific ecological interactions. PVs are important for pollinator attraction and have applications in flavoring, preservation, and herbal remedies. Flower and herb aromas may contain many individual chemicals, with little overlap in PV profiles between closely related species. The diversity of PVs suggests frequent changes in enzymatic profiles through evolution. Nonvolatile specialized metabolites also show diversity and rapid change, raising similar questions about evolutionary mechanisms. Advances in analytical techniques have made PVs one of the best-studied groups of plant secondary metabolites. The biosynthesis of PVs involves pathways derived from isoprenoid metabolism, including terpene synthases (TPSs) that produce diverse PVs. TPSs catalyze the formation of hemi-, mono-, sesqui-, and diterpene PVs from various precursors. TPSs have multiple functional variants, with some producing multiple products. PVs can also be derived from aromatic rings, phenylalanine derivatives, and type III polyketide synthases. Oxidative cleavage and decarboxylation of fatty acids produce shorter-chain volatiles. Some PVs are produced by cleavage of carotenoids or modified amino acids. Enzymes for PV biosynthesis often belong to large families, with some evolving from non-PV enzymes. Some modifying enzymes can use multiple substrates, and gene duplication and divergence contribute to functional divergence. Enzymes for PV biosynthesis often evolve from non-PV enzymes, with some P450 oxidases involved in PV biosynthesis. The spatial and temporal regulation of PV biosynthesis occurs in specific cells and tissues, with biosynthesis rates correlated with gene expression and substrate availability. Environmental factors such as light, temperature, and moisture influence PV biosynthesis, often following a rhythmic pattern. The transport, storage, and emission of PVs are areas requiring further study. Overall, PVs are diverse and play important roles in plant ecology and human applications. Many PVs and their biosynthetic enzymes remain to