All nucleocytoplasmic traffic of macromolecules occurs through nuclear pore complexes (NPCs), which function as stents in the nuclear envelope to keep nuclear pores open but gated. Three studies in this issue (Flemming, D., P. Sarges, P. Stelter, A. Hellwig, B. Böttcher, and E. Hurt. 2009. J. Cell Biol. 185:387-395; Makio, T., L.H. Stanton, C.-C. Lin, D.S. Goldfarb, K. Weis, and R.W. Wozniak. 2...