In the Görlich lab at the Max Planck Insitute for Biophysical Chemistry, we used nanobodies as tools to study nucleocytoplasmic transport - an essential process that sorts cytoplasmic and nuclear proteins to their correct subcellular compartment. Here, we used nanobodies as intracellular inhibitors of a nuclear transport receptor (NTR), which allowed us to demonstrate that the NTR Exportin 7 (Xpo7) could unexpectedly carry-out bidirectional protein transport. Using mass spectrometry, we identified numerous new import and export cargoes of Xpo7.