Nitric Oxide Synthase (NOS) is an enzyme responsible for producing nitric oxide (NO), a signaling molecule that plays a crucial role in various physiological processes. There are three main types of NOS: neuronal NOS (nNOS), endothelial NOS (eNOS), and inducible NOS (iNOS), each with distinct functions and locations in the body. Nitric oxide is important for regulating blood flow, neurotransmission, and immune responses. By relaxing blood vessels, NO helps to lower blood pressure and improve circulation. Additionally, it plays a role in the communication between nerve cells, contributing to processes like learning and memory.