The pathway Extracellular matrix organization is new and includes Activation of Matrix Metalloproteinases. Topics with new or revised events include Immune System (Regulation of complement cascade, Trafficking and processing of endosomal TLR, Signaling by B cell receptor, and DAI mediated induction of type I IFNs), Metabolism of proteins, (Mitochondrial Protein Import), Signal transduction (Signaling by Hippo, Signaling by Notch), Circadian clock, and Gene Expression (Regulatory RNA Pathways). Sean Egan is our external author. DT Bradley , G Butler, F Delaunay, HS Earp, T Endo, L Fraczek, CA Leifer, AM Misior, ES Mocarski, CM Overall, FJ Rauscher, WA Rose, M Sudol, Y Tomari, JW Upton, and J Wienands are our external reviewers. We have created short Reactome tutorial videos that demonstrate the use of our navigation and analysis tools. New ones for this release are Pathway Browser, Pathway Analysis, and Expression Analysis. Others will be added to the Reactome YouTube Channel as they become available. Our SBML export (available here) has been enriched with a wide variety of additional annotations, including SBO terms. We have switched from using the layout extension to embedded SBGN for conveying pathway layout.