Using a combination of quantitative single-cell structural and chemical imaging techniques, a collaboration of researchers from LPCV, IBS, Helmholtz Center, ESRF and other universities, show that the structural organization, physiology, and trophic status of the algal symbionts (the haptophyte Phaeocystis) significantly change within their acantharian hosts compared to their free-living phase in culture. This result, published in Current Biology, shed light on the functioning of this ecologically important cell-cell interaction and the subcellular mechanisms Press release (in french only).