Brexit — Britain's exit from the European Union — threatens to undermine the country's scientific relationships with nations outside the EU (see E. Masood Nature 535, 467; 2016). The country will need to invest more to maintain its valuable collaboration with China, for example, once EU funding is withdrawn.

The United Kingdom could be excluded from exchanges under the EU's Marie Skłodowska-Curie fellowship programme, which have benefited thousands of talented Chinese and British scientists since 2007. For the country to retain its current exchange level of international research talent, it would need to invest more in its Newton Fund to make up the shortfall (see go.nature.com/2bfgzq3).

Also under threat will be British scientists' participation in China's projects with the EU, such as its Five-hundred-meter Aperture Spherical Telescope, due to be completed this year (see W. Yang Nature 534, 467–469; 2016).

Despite such uncertainties, Brexit could still provide opportunities to strengthen scientific collaboration between the world's second and fifth largest economies — for example, through the collaboration between Research Councils UK and the National Natural Science Foundation of China (see go.nature.com/2bflysi).