To make a tree diagram in Excel you will need to utilize third-party diagramming tools, such as Lucidchart that allows you to create a tree diagram in Excel. These are known as add-ins to the program.

MS XML Notepad 2007<BR><BR>edit: just to clarify, this is an xml file editor that has a tree view pane on the left. You can right click and expand the whole tree, or leave it collapsed. More options ...

Take a look at this beautiful interactive tree of life diagram created by Evogeneao, which enables you to see how all organisms on earth are related, from humans all the way to ancient bacteria.