And the space, the fluid space between these two regions, the outer and the inner membrane, is known as the perinuclear space. Now, throughout the entire nuclear envelope, throughout the entire nuclear membrane, we have very tiny holes known as nuclear pores that basically allow materials to move into the nucleus as well as outside the nucleus. And we'll discuss exactly what the nuclear pore is in just a moment. Now, the outer membrane is actually physically connected to the membrane of the rough endoplasmic reticulum. And this is important because when we synthesize our RNA, ribosomal RNA, we have to have a quick way to transport our rRNA from the nucleus to our endoplasmic reticulum. And that's why they are connected.