Understand the definition of prokaryotic organisms: Prokaryotes are unicellular organisms that lack a nucleus and other membrane-bound organelles.
Identify the three domains of life: Bacteria, Archaea, and Eukarya.
Recall that the domain Eukarya includes all eukaryotic organisms, which have a nucleus and membrane-bound organelles, thus excluding them from being prokaryotic.
Recognize that both Bacteria and Archaea are domains that consist of prokaryotic organisms, as they do not have a nucleus or membrane-bound organelles.
Conclude that the two domains containing prokaryotic organisms are Bacteria and Archaea.