Around 4 billion years ago there lived a microbe called LUCA: the Last Universal Common Ancestor. There is evidence that it could have lived a somewhat ‘alien’ lifestyle, hidden away deep underground in iron-sulfur rich hydrothermal vents. Anaerobic and autotrophic, it didn’t breathe air and made its own food from the dark, metal-rich environment around it. Its metabolism depended upon hydrogen, carbon dioxide and nitrogen, turning them into organic compounds such as ammonia. Most remarkable of all, this little microbe was the beginning of a long lineage that encapsulates all life on Earth.