In eukaryotes DNA is tightly bound to histones which form a DNA protein particle called nucleosome. Each nucleosome contains two copies of each H2A, H2B, H3 and H4 histone proteins bounded on 146 b. p. of DNA. Each nucleosome bead is linked to next nucleosome bead by linker DNA. The chromosomes are nuclear components of Special organisation, individuality and function. They are capable of self reproduction and play a vital role in heredity, mutation and evolutionary development of species. Nucleolus was originally discovered by Fontana (1781) and the present name is given by Bowman (1840). It is naked roughly rounded structure attached to chromatin at nucleolar organiser region. Lysosomes are small vesicles containing hydrolytic enzymes. They contain about 40 acid hydrolases for digestion of various materials.