The nucleolus is surrounded by a thin nucleolar membrane. It is found in nucleus of eukaryotic cell.
The nucleus is a membrane-bound organelle found only in eukaryotic cells and it is considered control center of the cell because the whole genome is in it (excepting mitochondrial DNA). Nucleus contains domains or bodies, membraneless structures within it that make nucleus compartmentalized. The function of these “compartments” is to enhance the efficiency of nuclear processes. Nuclear bodies are:
• Cajal bodies- consist of proteins and RNA; its functions are associated with telomerase assembly; in cells that divide rapidly
• splicing speckles –contain RNA splicing factors
• promyelocytic leukemia protein nuclear bodies-involved in programmed cell death; control cell division.
• the nucleolus
Nucleolus is the largest structure in the nucleus which consists of proteins, DNA and RNA and it is the place where ribosome biogenesis occurs. This structure is also involved in the cell's response to stress.