Chlamydomonas reinhardtii has an eyespot similar to that of dinoflagellates(1). The eyespot is located near the cell equator. It is composed of a carotenoid-rich granule layer in the chloroplast which act like a light reflector.(2) The main function of the eyespot is the phototaxis, which consist of the movement (with the flagella) related to a light stimulus (3). The phototaxis is crucial for the alga and allows for localization of the environnement with optimal light conditions for photosynthesis. (4) Phototaxis can be positive or negative depending on the light intensity (1) .