Cells can increase in size through normal growth and cell division. Normal cell growth is due to metabolism, the cytoplasm of the material continues to accumulate and make the cell increase in size; while the cell mitosis process increases significantly in size, because this process of the cell to carry out pre-division preparatory work, including the replication of the genetic material DNA and synthesize proteins and other important substances, so that the cell contents within the stage will be increased significantly, the volume will also increase significantly. Cell growth mainly refers to the increase in cell volume, not all cells have growth process after the completion of cell differentiation, most of the tissues and organs are through continuous cell division to increase the number of cells to achieve organ growth, only a very small number of cells (e.g., neuron cells) is through the increase in cell volume to achieve organ growth.