The main portion of all cells is filled with a fluid material.Just like a human body, the interior of the cell contains food, waste material or even extra water . On the outside of all cells is a protective covering called a membrane.It is just like the shell of an oyster.Sometime cells divide in half, forming a new cell. In other word, one cell splits in half and an exact duplicate forms. Now there are two cell. When we are growing as a baby, cell division is responsible for mush of our growth