The animal kingdom is massive, but scientists know that they have only found a portion of its members. They are currently aware of about 2.3 million species—but that number increases by about 15,000 new additions per year, according to some estimates.
Researchers from 12 institutions in the US collaborated for years to document and quantify all of these animals, and created a comprehensive diagram to illustrate each known species and its evolutionary relationship to one another. Their work was published (paywall) last year in the Proceedings of the National Academy of Sciences.
Pretty freaking cool