We do not believe that it is feasible for a single organization to draw up a 'road map' for future light- and neutron-source facilities in the way that CERN does for the particle-physics community (see P. G. Radaelli Nature 505, 607–609; 2014). The diversity of the communities that use these facilities makes the centralization of scientific priorities impossible.

A range of research fields will benefit from Europe's investments in the X-ray Free Electron Laser and the European Spallation Source (ESS), and hundreds of scientists are collaborating to define ESS's capabilities and instrumentation (see go.nature.com/ip6afc).

Cassandras abound at the start of any large project that pushes the technological envelope, but the ESS is expected to boost scientific performance for neutron studies by as much as 300-fold, opening up entirely new fields of science.

Because the ESS forms part of a wider network of neutron and light sources, the discussion needed in Europe is how to leverage and integrate these sources most effectively to improve our research and economic environment.