[Summary] The Encyclopedia of Life (EOL) was launched in May 2007 as a global scientific effort to document all known species of animals and plants (1.8 million), including endangered species, and expedite the millions of species yet to be discovered and cataloged (6 to 8 million). The encyclopedia's honorary chair is Edward Wilson, professor emeritus at Harvard University, who, in an essay dated 2002, was the first to express the wish for such an encyclopedia. Technology improvements made it possible five years later with content aggregators, mash-up, wikis, and large scale content management. The multimedia encyclopedia has gathered texts, photos, maps, sound, and videos, with a webpage for each species, to provide a single portal for millions of documents scattered online and offline. The first pages were available in mid- 2008. The encyclopedia will be translated into other languages with the help of partner organizations. *** The Encyclopedia of Life was launched in May 2007 as a global scientific effort to document all known species of animals and plants. There are 1.8 million species, including endangered species, and millions of species yet to be discovered and cataloged, probably 6 to 8 million. This collaborative effort is led by several main institutions: Field Museum of Natural History, Harvard University, Marine Biological Laboratory, Missouri Botanical Garden, Smithsonian Institution, Biodiversity Heritage Library (BHL). The initial funding came from the MacArthur Foundation (US $10 million) and the Sloan Foundation ($2.5 million). A $100 million funding over ten years will be necessary before self-financing. The encyclopedia's honorary chair is Edward Wilson, professor emeritus at Harvard University, who, in an essay dated 2002, was the first to express the wish for such an encyclopedia. Technology improvements made it possible five years later, with content aggregators, mash-up, wikis, and large scale content management. Based on the work of thousands of experts around the globe, the multimedia encyclopedia will gather texts, photos, maps, sound and videos, with a webpage for each species. It will provide a single portal for millions of documents scattered online and offline. As a teaching and learning tool for a better understanding of our planet, the encyclopedia will reach everyone: researchers, teachers, students, pupils, media, policy makers, and the general public, who will be able to contribute in a wiki-style environment, with contributions checked by experts. As a consortium of the ten largest life science libraries, with other libraries to join in the future, the Biodiversity Heritage Library (BHL) started the digitization of 2 million documents from public domain spanning over 200 years. In May 2007, when the project was officially launched, 1.25 million pages were already digitized in London, Boston and Washington D.C., and available in the Internet Archive.