Nature, Published online: 28 October 2026; doi:10.1038/d41586-026-03294-7

Two archaeal strains that belong to a lineage closely related to the ancestor of eukaryotic cells (complex cells with membrane-bound organelles) have been brought into culture. Their simple internal organization, elaborate surface structures, microbial partnerships and protein-dependent lifestyle provide clues about how eukaryotic cells arose.