Each aspect of cell biology is amazingly complicated. However the ability to accurately copy the information stored in the nucleus, is particularly difficult. The giant polymerase molecules in the nucleus have the capacity either to duplicate the DNA (for cell division) or to copy it into RNA. This latter molecule then exits the nucleus and moves to the ribosomes for translation into proteins. This means that the proteins called for by the information in the nucleus, actually are produced in the cytoplasm (cell material outside the nucleus). A further complication is that anything passing into or out of the nucleus through the nuclear pore complex (NPC) must be provided with a unique add-on marker which the NPC will recognize. The whole process is highly precise and specialized.