The other day I got the July issue of American Scientist and was tickled to no end to see this portrait of mimiviruses on the cover. As I write in A Planet of Viruses, mimiviruses were literally hiding in plain sight for years. Scientists considered them to be bacteria because they were too big to be viruses (see the minuscule HIV and rhinovirus, the cause of colds, for scale). It turns out they are indeed viruses, and perhaps the most interesting viruses on Earth. They may even represent an ancient branch of the tree of life, reaching back several billion years. Check out James Van Etten's excellent review of the science of giant viruses in the magazine.