Living things are classified into three domains: bacteria, archaea and eukaryotes. The highest rank in a domain is the kingdom. Each kingdom has many smaller groups in it, called phyla. Each phylum has more smaller groups in it, called classes. This pattern looks like branches on a tree with smaller branches growing from them. Each species is put into a group because of what it does, how and what it eats, special body parts, and so on. At the end of the pattern, the groups (genera) are very small. Then each species in the genus is given its own name.