The parts of the cell nucleus are the nuclear envelope, the nucleoplasm, the chromatin and chromosomes and the nucleolus. The nucleus is likened to the "brain" of a cell; its activities control the actions of a cell.
A nuclear envelope surrounds the nucleus. This membrane consists of two layers and contains holes called nuclear pores that allow certain substances to enter and exit the nucleus. The nuclear envelope merges with the endoplasmic reticulum to facilitate the transport of substances. A thick fluid called the nucleoplasm bathes structures within the nucleus.
The nucleus contains the blueprint of life called deoxyribonucleic acid, or DNA. Structures called chromosomes house the DNA. The chromosomes are usually condensed into structures called chromatin to save space.
The nucleolus is a spherical structure that assembles ribosomal parts. The ribosomes are organelles that make proteins. Once ribosomes are made, they pass through the nuclear membrane and reside in the cytoplasm.