Can substances move in and out of the nucleus?

Yes, substances can move in and out of the nucleus through nuclear pores. Nuclear pores are small channels that extend across the nuclear envelope and allow substances to enter and exit the nucleus. Each pore is lined with a structure of 50 to 100 different proteins, known as the nuclear pore complex. The pore complexes regulate the movement of macromolecules, proteins, and RNA into and out of the nucleus. This process is known as nuclear transport. Thus, the nuclear pores are highly selectively permeable as to what it allows in and out of the cell. They allow passage of molecules by either passive diffusion or facilitate translocation.