A cell is the basic unit of living organisms (both plants and animals)
that is capable of reproducing itself exactly.
The nucleus is the "Control Center" of each cell, which
contains DNA (deoxyribonucleic acid, which is genetic information)
in the form of genes, and also information for the formation of proteins.
DNA, which is combined with protein, is normally dispersed throughout
the nucleus as chromatin. During cell division the chromatin becomes
visible as chromosomes.
The nucleus also contains ribonucleic acid
(RNA), most of which is located in the nucleolus.
See the Revision page about Cell
Structure for further information including a diagram of the
structure of a basic cell including ribosomes and other organelles.