Giant DNA viruses make big strides in eukaryote evolution.

Nucleocytoplasmic large DNA viruses (NCLDVs) are widespread in the biosphere. This issue of Cell Host & Microbe, Nelson et al., and a recent Nature paper, Moniruzzaman et al., show NCLDVs can integrate into host genomes, highlighting a mechanism of large-scale virus-mediated horizontal gene transfer (vHGT) driving eukaryotic evolution.