You can build a tree for your own selection of organisms or taxa by either of following two methods.
By default dispalyed Common Tree consists of only nodes with the following taxonomic ranks:
You can also use ENTREZ TAXONOMY to build a tree for user defined organisms.
Any tree that you build with this tool is based on the classification in the NCBI taxonomy database, which is derived from a diverse array of phylogenetic resources. Because of this, please be aware that your trees may contain errors or inaccuracies. The tree display is a tool for exploring data but it cannot replace a careful phylogenetic analysis of molecular or morphological characters.