The eyespot is an organ that helps in light reception and is usually present in unicellular organisms and some multicellular invertebrates.
The eyespot is also present in Euglena, which is a green unicellular organism and the eyespot helps it to receive and detect light.
The light detection helps the euglena to move as the eyespot is located at the base of the flagellum and this eyespot helps influence the flagellar motion.