Opsin is a type of protein found in the photoreceptor cells of the retina in the eyes of many animals, including humans. These proteins play a crucial role in the process of vision by detecting light and converting it into electrical signals that the brain can interpret. There are different types of opsins, each sensitive to specific wavelengths of light, allowing for color vision and the ability to see in varying light conditions. In addition to vision, opsins are also involved in other biological processes, such as regulating circadian rhythms and influencing behaviors in response to light. They are part of a larger family of proteins known as G-protein coupled receptors, which are important for cell signaling. Research on opsins continues to provide insights into both vision and broader physiological functions.