Carolus Linnaeus developed the modern system of scientific classification of organisms that is still used today. His system was based on grouping organisms with similar structures together. He also established binomial nomenclature, the two-word scientific naming system where the first word is the genus and the second describes a distinguishing feature of the species. Modern classification builds on Linnaeus' work by also considering fossils, genetics, and development to classify organisms into a hierarchical grouping from species to kingdom.