Production processes are fragmenting across borders with countries trading tasks rather than products. Export statistics based on value added reveal a process of vertical specialisation. Yet, what do countries do when exporting? In this article, we provide novel evidence on functional specialisation (FS) in trade. We find surprisingly large and pervasive heterogeneity in specialisation across countries. A positive (negative) correlation between GDP per capita and specialisation in R&D (fabrication) functions is documented. Specialisation in management and marketing functions is unrelated to income. We show how our approach can be easily extended to study FS in trade at the sub-national level. We argue that this is needed to better under...