Photosynthetic micro-organisms contribute for half of dioxygen production, consume carbon dioxide, and are promising regarding biofuel production. Our lab aims to develop a quantitative approach describing the energetic state of these micro-organisms exploring their environment, a crucial aspect to better understand their motility behaviour. To tackle this problem, we use the motile micro-algae Chlamydomonas reinhardtii, a model unicellular organism, per-forming photosynthesis (light-to-chemical energy conversion) and phototaxis (cell reorientation along the light direction). Two projects are available.