Each about one micron—a thousandth of a millimeter—in length, the newfound genus Pandoravirus dwarfs other viruses, which range in size from about 50 nanometers up to 100 nanometers. A genus is a taxonomic ranking between species and family.

In addition to being huge, pandoraviruses have supersize DNA: 2,500 genes as compared with 10 genes in many viruses. (Get a genetics overview.)

Microbiology was similarly upturned about ten years ago when scientists found the genus Mimivirus—the first large virus of its kind at about 0.7 micron.

Following the discovery of Mimivirus and an even larger behemoth called Megavirus chilensis, "we have been thinking deeply into the limits of viruses, and this is why we're open more than other labs to finding exotic things—we