This is just mind-blowing. In the link is a pretty decent explanation of the research, as well as links to the papers and a video interview with two of the (many) authors.
The nuclear pore complex (NPC) is the gatekeeper of the nucleus. Eukaryotic cells (including the cells that make up humans and other higher organisms) contain a nucleus which contains the cell's genome. The nuclear envelope is the barrier which encases the genome, however it has to be selective in what it keeps in or out. In other words it has to somehow let in specific molecules that are necessary for a huge number of nuclear processes, and allow other molecules to exit. The way it does this is through NPCs. NPCs poke big holes in the nucleus, but act as the gatekeepers of these holes. They prevent molecules from entering or exiting the nucleus unless they have a ticket, er, actually, that is, unless they are associated with transport proteins.
Anyway, the NPC is too big to get a crystal structure, but still sub-microscopic enough that it is hard to make out the fine details like where specific components are. This study was a real tour de force because it compiled molecular restraints from biochemical and proteomic experiments into a program that generated a most likely conformation of the NPC. It's a thing of beauty too. It's like a donut with spaghetti in the middle. The spaghetti is too thick for large molecules to pass through, while little ones can squeeze through with ease. Additionally, if a molecule is associated with the right transport factor (or if it has a ticket), the spaghetti lets it pass. Donuts and spaghetti! It makes perfect sense!