Euplotes spread into every aquatic habitat of our planet and diversified into dozens of species that can promptly be identified taxonomically on the basis of well‐established diagnostic traits related to their ciliary and cortical structures. In large numbers, they can be easily collected and cultivated in laboratory for years with no apparent sign of senescence and decline. They are a rich source of secondary metabolites of terpenoid nature, host symbiotic bacteria in their cytoplasm and manifest sex in the form of conjugation and, more exceptionally, autogamy. Owing to their capacity to synthesise families of diffusible protein pheromones in functional association with their high‐multiple mating systems, Euplotes species provide valuable experimental material to study the molecular basis of self/nonself recognition phenomena in early forms of the eukaryotic life.