The nucleus is the innermost sanctuary of the eukaryotic cell. Nuclear pore complexes (NPCs) embedded in the double membrane of the nuclear envelope function as guards to this sanctuary, controlling import and export of molecules into and from the nucleus.

The NPC of eukaryotic cells consists of about 30 proteins collectively termed nucleoporins that assemble into a huge structure of over a 100 million Daltons. Progress in the elucidation of the function and structure of the nucleoporins will be discussed.