On April 19th, our work was published in Nature. In this work, we discovered a novel group of large DNA viruses dubbed “Mirusviricota“. Most of double stranded DNA viruses are classified into one of two realms: Varidnaviria, which includes giant viruses, and Duplodnaviria, which includes herpesviruses causing diseases in animals. These two realms have been considered evolutionarily unrelated. However, the newly discovered mirusviruses possess features of both realms. Genes of “informational module” for genome replication and gene expression were similar to those of Varidnaviria, while genes of “virion module” that encode structural proteins were similar to those of Duplodnavira. This mosaic feature of mirusviruses suggests that herpesviruses evolved from tailed bacterial viruses via ancestral protist-infecting viruses, namely the ancestors of the modern day mirusviruses and herpesviruses. Furthermore, gene transfers of “informational genes” between the two realms probably played crucial roles in their evolution. Mirusviruses appear to be prevalent and abundant in the sea and likely infect a variety of protists. However, they were discovered by bioinformatics analyses of marine metagenomic data, and there are currently no cultured viruses from this group of viruses. This work was achieved by a collaboration with groups of scientists in France and Denmark.