STRING is a database of known and predicted protein-protein interactions. The interactions include direct (physical) and indirect (functional) associations; they stem from computational prediction, from knowledge transfer between organisms, and from interactions aggregated from other (primary) databases. The STRING database currently covers 59'309'604 proteins from 12'535 organisms. STRING Database is supported by organisations including Swiss Institute of Bioinformatics, Novo Nordisk Foundation CPR, University of Zurich, EMBL Heidelberg, Scientific Advisory Board.