There are three main branches to the ‘tree of life’: bacteria, eukaryotes (including plants, animals and fungi), and archaea. The last of these is the least well known, and archaea were only established as a distinct lineage in the 1970s. Many archaeal species are found living in extreme conditions, at high temperatures, in acidic pools or in salt crystals. My lab specialises in developing new techniques in microscopy and applying these to understand how microbes move around and survive in the wild. I will discuss some of our field work at Great Salt Lake in Utah (USA), and in Boulby Mine in Redcar and Cleveland (UK). We isolated strains of archaea from both locations, sequenced their genomes and studied their swimming patterns in 3D using our holographic microscope. Intriguingly, they have ‘repurposed’ genetic components from bacteria to their own ends, and through computer simulations we have been able to show that their swimming behaviour and navigation strategies are right at the physical limit of what is physically possible in harsh, nutrient-poor environments.