Proteins from outside a cell that stimulate it to divide are called growth factors.

Here's why:

* Growth factors are signaling molecules that bind to specific receptors on the cell surface, triggering a cascade of intracellular events that ultimately lead to cell division.

* They are essential for normal cell growth, development, and repair.

* Examples include epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF).

Let me know if you have any other questions!