Each cell of your body has a life span and as each cell dies, another must take its place. All cells start out as exactly the same type of cell, but at some point they become 'different' from each other; a hair cell, a liver cell, a skin cell, etc. To become different they need the instructions of what kind of cell to become. Those instructions come in the from of 'Growth Factors' (GFs) and travel from the dying cell to the new, baby cell in tiny spherical packages like the o