Ever since living organisms arose in the oceans, they have competed for resources and space. However, many planktonic species developed peaceful cooperation involving mutualistic interactions between two partners. Within unicellular eukaryotes, such symbiotic association between heterotrophic hosts and microalgae is widespread and sustain ecologically important taxa, such as the Rhizaria, in the open ocean. While knowledge of bipartite symbiosis has greatly improved, it is only recently that scientists disclosed more intricate relationships involving additional partners such as bacteria. Wherever bacterial communities (i.e. microbiota) have been found in tight association with other organisms (e.g. humans or plants), its critical role for the biology and ecology has been demonstrated. The DYNAMO project explored the diversity of multipartite symbiosis in the plankton and aimed at characterizing the cellular metabolites they produce. Radiolarians have been used as relevant model for marine ecology. An original combination of single-cell sorting and sequencing coupled with microscopy has been used to characterize and specifically localize the partners of the association. Then, a cutting-edge approach of single-cell genetics and of metabolomics, allowed us to better describe the bacterial diversity and better understand the role of the associations in the physiology of the holobiont. We tried to bridge the gap between a descriptive approach and the functional understanding of the biological processes involved in plankton associated microbiota. DYNAMO provided an innovative perspective on marine ecological research and represented an important step in my career development with the ambition to place me as one of the very few experts in the field of plankton metabolomics in Europe.