The complex structures of proteins enable their many biological functions, most of which include selective interactions with other molecules, i.e., molecular recognition. The variety of recognition motifs, the range of binding affinities, and the fidelity of recognition displayed by proteins are truly remarkable and enable biological processes as diverse as cellular respiration, transport, signaling, metabolism, and the immune response, to name a few. In parallel with the efforts to characterize biomolecular recognition mechanisms, chemists have attempted to mimic them using designed small molecules and selected biological molecules (e.g., monoclonal antibodies, nucleic acid aptamers, display peptides). Indeed, the molecular recognition of proteins has been a challenge in chemistry for several decades and has led to the fields of drug design, biosensors, clinical diagnostics, bioseparations, biomaterials, and other areas of chemical biology.^1–8  Despite the extensive efforts and many successes to date, much remains to be understood about the interactions within and between the surfaces of proteins and the principles by which synthetic agents can be designed to efficiently imitate them. There are many reviews on this subject. The current chapter focuses on the unique properties of aromatic amino acids that have enabled their recognition by biological and synthetic receptors. Inquiries into the nature of aromatic interactions and the roles they play in biological recognition have been reviewed extensively elsewhere.^9–15  Select examples will be discussed here to illustrate the roles of aromatic residues in biological recognition before discussing in greater detail the development of synthetic receptors for proteins and peptides, and the lessons learned from those studies.