Non-globular FG domains constitute the permeability barrier of nuclear pore complexes (NPCs), which control all macromolecular exchange between nucleus and cytoplasm. Whilst objects smaller than 30kDa can passively diffuse across this barrier, larger molecules need to be chaperoned by nuclear transport receptors (NTRs). However, the modus operandi and, inextricably linked, the exact physical nature of the NPC permeability barrier are still controversially discussed. Whereas so far, most studies exclusively focused on yeast or vertebrate FG domains, the ability of FG domains from different species to form selective barriers was explored here. Interestingly, all studied species contain 'cohesive' FG domains that interact with each other to form a characteristic (hydrogel) phase mimicking the permeability properties of NPCs.