After his student years, Olav Giere investigated on sampling campaigns and student excursions the ecology of microscopic organisms living in the sediments of North Sea shores. Early on he studied in fieldwork and experiments the impact of disastrous oil spills on marine fauna. Interested in the multiple interactions of function and form of sediment fauna, he then focussed on the ecology and adaptations of animals living in low-oxygen/high-sulphide conditions. In many cases, meiofauna is adapted to these conditions occurring in shallow sites, at the deep-sea floor, and in subterranean waters. This lead Giere to research and teaching stays in different countries, but also to several deep-sea and cave expeditions. On Bermuda he discovered exotic gutless meiobenthic worms living in an obligate symbiosis with ‘sulphur bacteria’. These studies sparked new, far-reaching research fields on novel symbiotic pathways under unusual ecological conditions. Based on his comprehensive textbook Meiobenthology (2nd revised edition in 2009) – the science of microscopic, ubiquitous animals – the author now presents a summary and appraisal of the recent situation in this often neglected research field and works out recommendations for its scientifically successful future.