Signaling molecules are chemical substances that facilitate communication between cells in the body. They play a crucial role in various biological processes, including growth, immune responses, and metabolism. Examples of signaling molecules include hormones, neurotransmitters, and cytokines, which help transmit messages and coordinate activities among different cells. These molecules can bind to specific receptors on target cells, triggering a response that can alter the cell's behavior or function. This process is essential for maintaining homeostasis and ensuring that the body responds appropriately to changes in the environment or internal conditions.