EMPIAR, the Electron Microscopy Public Image Archive, is a public resource for raw, 2D electron microscopy images. Here, you can browse, upload, download and reprocess the thousands of raw, 2D images used to build a 3D structure. The purpose of EMPIAR is to provide an easy access to the state-of-the-art raw data to facilitate methods development and validation, which will lead to better 3D structures. It complements the Electron Microscopy Data Bank (EMDB), where 3D images are stored, and uses the fault-tolerant Aspera platform for data transfers. EMPIAR is based on input from the EM community, notably at two key workshops organized by the Protein Data Bank in Europe (PDBe) and the Open Microscopy Environment (OME) - ”Data Management Challenges in Three-dimensional EM” (Patwardhan et al., Nat. Struct. Mol. Biol. 19, 1203-1207 (2012)) and ”A 3D Cellular Context for the Macromolecular World” (Patwardhan et al., Nat. Struct. Mol. Biol. 21, 841-845 (2014)).