Virology-the study of entities existing between the living and nonliving words-has long intrigued and mystified biologists.  Seven years ago, researchers discovered giant viruses, with more than a million nucleic acid bases containing more than a thousand genes.  This piece reports that viruses may have started off in larger forms, before living cells existed, and gradually broke apart into smaller entities.  Quite certainly, untold numbers of new viruses are yet to be discovered.  MORE