From the website:
This picture is a visualisation of the entire tree of life. The tree of life (cellular organisms) has three main branches:
* The bacteria (unicellular prokaryotic microorganisms) which are in focus in this picture and represented by orange nodes.
* The archaea which are probably more closely related to the eukaryotes than they are to the bacteria even though they lack a cell nucleus and represent some of the most extreme forms of life on earth. They are represented by red nodes and near the top and in the background of the picture
* The eukarya (all cellular organisms with a cell nucleus) represented by yellow nodes and are located on the left hand side and in the background of the picture.