Robert Brown (1831) discovered nucleus in cells of an orchid. It is the principal organelle of the cell. The membrane-bound nucleus is the most prominent feature of the eucaryotic cells. In prokaryotic cells it is membraneless but performs similar function.
The difference between Nucleus and Nucleolus is that Nucleus is a large spherical structure present in the cell whereas Nucleolus is very small and is present inside the nucleus.
The difference between Nucleus and Chromosome are Nucleus is a cell organelle Chromosome whereas is present in the nucleus. Nucleus has nuclear membrane, nucleoplasm, chromatin network and nucleolus but choromosomes have two chromatids, which are held at cetromere.
The prominent spherical structure present within a living cell is the nucleus, which is controlling center of the cell. A typical eukaryotic nucleus is separated from cytoplasm by nuclear membrane.
Nucleus is a specialized protoplasmic body which is usually spherical or oval in shape and is much denser than the cytoplasm. In the young cell, it occupies a median position. In the mature plant cell, with the formation of the vacuole, it lies in the lining layer of the cytoplasm.
The nuclear composition is expressed in terms of the neutrons and protons in the nucleus, or, as the atomic number (Z) and mass number (A). The number of protons present in the nucleus of an atom represents the atomic number of the atom. It is denoted by the capital letter, Z.