Margaret Oakley Dayhoff was a researcher in the United States during the twentieth century who studied physical chemistry and the application of computers to biological problems such as the analysis of protein structure and function. Proteins are molecules that perform work in cells and are made up of subunits called amino acids arranged in a particular sequence. In the 1960s, researchers were cataloguing new protein sequences at an accelerating rate, and a database did not yet exist to contain them. In response, Dayhoff collected and made available all known protein sequences in her book Atlas of Protein Sequence and Structure and later in the electronic database called the Protein Sequence Database. Her work on data collection provided the foundation for UniProt and GenBank, which, as of 2026, are international and free databases of all known protein and nucleic-acid sequences, respectively. Through the databases and computer programs she created, Dayhoff provided researchers the tools they needed to better understand the evolutionary relationships among all biological life.