Non-technical summary: The Aegean region is located in the eastern Mediterranean region and encompasses Greece, the Aegean Sea and western Turkey. It is one of the seismically most active regions in the world, due to interaction between the surrounding Eurasian, African and Arabian tectonic plates. Where and how this deformation is being accommodated has been subject of debate for a long time. We use GPS measurements of movements of the Earth's surface obtained during the last decades to show that the predominant part of the intraplate motion is taken up along the boundaries of four microplates that cut up the Aegean crust. From these results we infer that the highest earthquake hazard is expected to be similarly localized along these microplate boundaries.