Eukaryota
Eukaryota, and also Eukariota, Eukaria or Eukarya, from the Greek eu, true, and karyon, nut, here in reference to nucleus, usual and informally called as the eukaryotes, in scientific classification, is a domain formed by all living beings composed by cells where there is a nucleus, with various organelles, enclosed by a membrane that separates its content from the surrounding cytoplasm. These organisms vary since unicellular to very complex individuals with many different types of cells carrying particular functions.
Almost all living beings belong to Eukaryota, except Bacteria and Archaea, which are the two other domains of organisms that can live independently, without another cell as a host. Viruses cannot live independently; prions are even more questionably forms of life rather than chemicals that affect life.
Domain Eukaryota is divided in kingdoms: