The basic unit in the human body is a cell that combines with other cells to form tissues, organs and systems. There is a continuous process going on in the body where old cells keep dying and new ones are produced. This replacement takes place through a process called mitosis that results in the division of the old cell into new ones. The cells have all the information in them so that at the time of division, there is no need for any other stimulus. As I have said earlier, cells are the basic building blocks of human beings and they carry all the information necessary for the survival of that cell. Due to this information, it carries out all the processes like energy production, waste disposal and division on its own. The new cells produced are identical to the older ones, this reduces chances of mutations. If it had not been so then each and every cell in the body would need the help of a central system which would have considerably slowed down the process.