Nature Protocols is pleased to be a part of the Resource Identification Initiative, a project aimed at improving the reproducibility of research by clearly identifying key biological resources. Stable unique digital identifiers, called Research Resource Identifiers (RRIDs), are assigned to individual resources, allowing users to accurately identify and source them, track their history, identify known problems (such as cell line contamination and misidentification) and find relevant research papers. Following a successful 6-month trial, we will now require authors to provide RRIDs for all antibodies and cell lines used in their protocols. We will also be encouraging them to add RRIDs for other tools (such as plasmids and organisms) where they think this is helpful.