What are the three major features of the nucleus?

The three major features of the nucleus are the nuclear envelope, nucleoplasm, and nucleolus. The nuclear envelope is a double membrane that surrounds the nucleus, containing nuclear pores for material exchange. Nucleoplasm is the semi-fluid matrix within the nucleus, providing a medium for biochemical processes. The nucleolus is a dense structure responsible for ribosomal RNA synthesis and assembly of ribosome subunits.