The MI group released an XML standard (PSI-MI XML) as early as 2004, which allowed the basic information about a protein-protein interaction experiment to be captured and transferred between data resources or visualization/analysis tools. This initial, very simplistic representation was very soon upgraded to enable a full capture of the details of any experiment, including in silico and predictive data, which describes an interaction between any number of biomolecules, including experimental details, molecule details (affinity tags, binding sites, amino acid mutations, etc.), and the host organism in which the experiment is undertaken. Additional information, such as kinetic parameters or the method by which a molecule is delivered or engineered into a cell can also be added, if required. The PSI-MI XML2.5 version of the format remains the main workhorse by which the majority of interaction data is exchanged between resources, and enables all of the above use cases. As more specialist use cases have arisen which could not be fully captured in this format, in 2018 a new, backwards compatible version, PSI-MI XML3.0, was developed. This version can be used to describe, for example, the details of a fully curated multiprotein complex with subunit topology, including binding regions, and stoichiometry or to link kinetic parameters to amino acid mutations, sequence deletions or insertions.