In eukaryotic cells, molecules can only move into or out of the nucleus through specialized channels called nuclear pore complexes (NPCs). Each NPC has a ring of nucleoporin proteins flanking either end of the central channel, which usually share an identical structure. But in fission yeast Schizosaccharomyces pombe, researchers have found that the NPC outer ring structures are completely asymmetrical, shedding new light on the structure and function of the nucleus.