Growth factor

A growth factor is something in the body that allows or deny cells to grow. These factors are normally made up of cell hormones or other proteins within the body. All growth factors occur naturally within cells and are necessary for the cell life progression and death. 
History.
The first growth factor discovered and publicly recognized was in 1986. It was recognized in the form of a Nobel Prize. The award was given to Rita Levi-Montalcini and Stanley Cohen.