Mussels are masters of wet adhesion, employing very specialized proteins with unusual biochemical properties and amino acid compositions. The attachment organ of the mussel, the byssus, contains several proteins rich in 3,4-dihydroxy-L-alanine (DOPA), a catecholic amino acid that is believed to confer cohesive and adhesive properties to these proteins. In this talk I will discuss the role of DOPA in mussel adhesion, including model studies of catechol cross-linking and single molecule force spectroscopy measurements that shed light on the interfacial role of DOPA and other key amino acids found in these proteins. Our experiments provide insights into key mechanisms of biological adhesion, and also inform the design of synthetic mimics of these proteins. Examples of biomimetic materials include surgical adhesives, and coatings for a variety of uses. Finally, I will briefly introduce our related work with polyphenols found in tea, chocolate, red wine and other foods and beverages. Plant polyphenols are chemically similar to DOPA due to an abundance of resorcinol, catechol and gallol functional groups, and therefore can be exploited in similar ways as DOPA.