Nuclear pores control the movement of substances into and out of the nucleus of a cell: 

Transport: Nuclear pores allow specific molecules, like RNA and proteins, to move between the nucleus and the cytoplasm in both directions. 

Direction: Nuclear pores transport substances in one direction, like carbohydrates, lipids, and signaling molecules into the nucleus. 

Water-soluble molecules: Nuclear pores allow water-soluble molecules to cross the nuclear envelope