The biosynthesis of shikimic acid is a central biochemical process that forms the basis for the production of aromatic amino acids and their derivatives, which are explained in this chapter. These amino acids, including phenylalanine, tyrosine, and tryptophan, serve as precursors for a variety of secondary metabolites, such as alkaloids, flavonoids, and cinnamic acid derivatives. Technically important compounds like lignin and tannins can also originate from the shikimate pathway. Most phenolic natural substances are biosynthesized from aromatic amino acids and, play an important role in the plant kingdom, and also occur in petrochemical products. They can occur freely or bound to sugar and are often structurally modified. Plant phenols, characterized by an aromatic ring and a propane side chain, are also used in the food and cosmetics industry. Some of these compounds have pharmacological effects, but can also be toxicologically problematic. Technically relevant examples such as vanillin, podophyllotoxin, tannins, and lignin illustrate the diversity and potential effects of these natural substances, whose biosynthesis and biotechnology are intensively discussed in this chapter.