Molecular signals are chemical messages that cells use to communicate with each other. These signals can be hormones, neurotransmitters, or other molecules that bind to specific receptors on target cells. This binding triggers a response, allowing cells to coordinate activities such as growth, immune responses, and metabolism. In multicellular organisms, molecular signals play a crucial role in maintaining homeostasis and regulating physiological processes. For example, the insulin molecule helps control blood sugar levels by signaling cells to absorb glucose. Understanding these signals is essential for fields like biochemistry and pharmacology, as they can influence drug development and disease treatment.