Phenols are important components of biological tissues, where they perform a variety of biological functions including chemical defense, redox and antioxidant properties, pigmentation, and bioadhesion. One of the most important families of phenols are catechols (ortho-dihydroxyphenyls), which in humans take the form of neurotransmitters and the main building blocks of melanin pigments. However, the catechol functional group is rarely found in structural proteins with the exception of marine adhesives. Celebrated examples are the proteins of the byssus, the attachment organ of the mussel. Some byssal proteins contain high levels of the catecholic amino acid 3,4-dihydroxy-L-alanine (DOPA). DOPA is believed to contribute to both the interfacial and bulk mechanical performance of the tissue. Satisfying such diverse roles is only possible because catechols participate in a remarkably broad range of chemical interactions that include noncovalent coordination interactions with metals/metal oxides, strong hydrogen bond, cation-pi and pi-pi interactions, redox activity, and covalent coupling with nucleophilic organic species. In this talk I will review what is known about the function of DOPA in the mussel byssus and describe ongoing efforts focused on the mechanochemical behavior of DOPA at solid-liquid interfaces. Emphasis will be placed on mechanical characterization across length scales, from single molecule to macroscopic adhesion methods. These studies are informing the development of novel functional materials for a variety of applications, and I will provide a few selected examples of how we seek to exploit catechols as building blocks of synthetic bioinspired adhesives, hydrogels and coatings.