Researchers in Hong Kong and the UK have revealed how one species of self-propelling microbes can actively change the path of their swimming motions, depending on how much light they receive. Reporting in Physical Review Letters, a team led by Zhao Wang at the University of Hong Kong shows that the switch arises as the microbe alters the beating pattern of its hair-like flagella, possibly allowing it to optimize the amount of light it absorbs for photosynthesis.