The Encyclopedia of Life Sciences volumes 1-26 comprises the original 20 volumes of ELS (published in 2002) plus six supplementary volumes (published in 2007). Volumes 21-26 collates all the information that has been added to the online version on WileyIntersciences since the publication of the first 20-volume set. Together, they provide the reader with the most comprehensive and the up-to-date information in Life Sciences.