After many years working on Chlamydomonas, we finally graduated to multiple cells… But from a different organism: Volvox carteri. This multicellular relative of Chlamy has thousands of biflagellate somatic cells on its surface, which can be easily extracted from the colony and keep on beating for several hours. We grabbed two with independent micropipettes and showed that below a critical separation, the cells synchronise their beating. Synchronisation has a purely hydrodynamic origin. At the same time, their interaction changes the waveform of their flagella. Flagellar elasticity cooperates with hydrodynamic stresses to generate synchrony as predicted a few years ago!