The nuclear envelope is a double membrane structure that surrounds the nucleus of a cell. It consists of two lipid bilayers, the inner and outer membranes, which help protect the genetic material inside the nucleus. This barrier regulates the movement of substances in and out of the nucleus, allowing essential molecules like RNA and proteins to pass through while keeping the DNA safe. The nuclear envelope is punctuated by nuclear pores, which are large protein complexes that facilitate the transport of molecules. These pores play a crucial role in maintaining the cell's functions by controlling the exchange of materials between the nucleus and the cytoplasm, ensuring that the cell operates efficiently.