Cells do not arise de novo but are formed from preexisting cells by reproduction”, is one of the important attributes of the modern cell theory. Accordingly, every multicellular organism, be it microscopic, or macroscopic begins its existence as a single cell. This undergoes successive cycles of cell reproduction till an adult is formed. In a cell there exists a balance between the cytoplasm and the nucleus and the cell continues to grow till this balance is maintained.
Continued growth of the cell culminates in partitioning of cytoplasm and nucleus into two daughter cells by cell division. Besides, cell division is essential for continuity of life.
Despite its complexity, cell division is a mistake-free and coordinated process. It involves three major steps like replication of DNA, division of nucleus and division of cytoplasm. Of these, division of nucleus is known as karyokinesis and that, of cytoplasm, cytokinesis. Somatic cells divide by mitosis whereas germ cells are formed through meiosis.