What are the 3 biological domains?

Archaea, Bacteria, and Eukarya. Archaea are some of the oldest single celled organisms on the planet due to their capability to survive in extreme conditions. Bacteria, also called eubacteria or true bacteria, are composed of prokaryotic cells, but their cell walls have different structures, components in them. Eukarya are composed of eukaryotic cells and contain most the multicellular organisms in our world such as animals, plants, protists, and fungi. Hope this helps.