During Linnaeus's time, taxonomy only had two kingdoms: plant and animal. In this topic, you have learned that the classification of organisms has become more complex. The three domains of Bacteria, Archaea, and Eukarya are further classified into the kingdoms Bacteria, Archaea, Protista, Fungi, Plantae, and Animalia. The kingdoms are even further divided into phyla, classes, orders, families, genera, and species.