The Human Proteome Organization (HUPO) Proteomics Standards Initiative (PSI) was formed 20 years ago in 2002, under the leadership of Rolf Apweiler, Ruedi Aebersold, and others committed to the formation of an organization that would develop standards for the field of proteomics. At the time there were only vendor formats for raw mass spectrometry data and a few over-simplified plain text formats specific to the software tools of the time. Yet it was recognized that standardized formats would allow not just tool interoperability, but also promote the sharing and reuse of data between laboratories.