Classification involves assigning organisms to taxa based on similarities and differences. Carl Linnaeus established the system of binomial nomenclature, giving each organism a genus and species name. Organisms are classified into a hierarchy of domains, kingdoms, phyla, classes, orders, families, genera, and species. The six kingdoms are Archaebacteria, Eubacteria, Protista, Fungi, Plantae, and Animalia. Plants are multicellular organisms that photosynthesize and are divided into nonvascular and vascular groups.