The nucleus of eukaryotic cells is surrounded by a double membrane structure, the nuclear envelope, that is punctuated by nuclear pore complexes. During interphase, nuclear pores represent the exclusive sites of transport between the nucleus and the cytoplasm. Are these nuclear pore complexes generated by splitting of existing pores, or are they produced de novo? D'Angelo et al. (p. 440) present real-time imaging of nuclear pore complex assembly in living cells and suggest that nuclear pore complexes form de novo and are assembled from both sides of the nuclear envelope.