History of the classification of Bacteria and Archaea. Time span Classification mainly based on Late 19th century Morphology, Growth Requirements, Pathogenic potential 1900–1960 Morphology, Physiology, Biochemistry 1960–1980 Chemotaxonomy, Numerical Taxonomy, DNA–DNA Hybridization 1980–today Genotypic Analyses, Multilocus Sequence Analyses, Average Nucleotide Identity, Whole Genome Analysis References