A growth factor is a naturally occurring substance that stimulates cellular growth, proliferation, and differentiation. These proteins play a crucial role in various biological processes, including tissue repair, immune response, and development. Growth factors bind to specific receptors on the surface of cells, triggering a series of signaling pathways that lead to changes in cell behavior. Common examples of growth factors include epidermal growth factor (EGF) and nerve growth factor (NGF). They are essential in both normal physiological functions and in medical applications, such as wound healing and cancer treatment. Understanding growth factors is vital for advancements in regenerative medicine and biotechnology.