The discovery of mimivirus in 2003 broadened the frontier of virology by revealing the existence of giant viruses with particle sizes and gene contents akin to that of cellular microbes. Sampling expeditions revealed that mimivirus relatives were abundant in the environments where they infect unicellular eukaryotes and are active players in all ecosystems. The infectious cycle of mimivirus and specific features of its virion will be presented. Members of other families were isolated using the same sampling strategies, including the Marseilleviridae and the surprises their study revealed. As we thought we were finally reaching the limit of viral complexity, members of the Pandoraviridae revealed over 1 micron-long particles packing genomes up to 2.8 Mb encoding a vast majority of proteins unique to the family. Finally, sampling >30,000-year-old permafrost samples led to the reactivation of an ancient pithovirus and mollivirus sibericum on modern amoeba. The new Pithoviridae family rapidly increased with ancient and modern members now dividing the family into 3 clades. There is only one additional modern mollivirus isolated so far. To conclude, I will briefly present recent findings on mimivirus infectious cycle questioning the origin and evolution of DNA viruses and their possible link to the emergence of eukaryotes.