The principle of openness is enshrined in CERN’s founding Convention, and all LHC publications have been published Open Access, free for all to read and re-use. The first high-level and analysable collision data openly released come from the CMS experiment and were originally collected in 2010 during the first LHC run. “This is all new and we are curious to see how the data will be re-used,” says CMS data preservation coordinator Kati Lassila-Perini.