The evolution of tetrapods (land vertebrates) from lobe-finned fishes, nearly 400 million years ago, was a hugely important event.For one thing, if these ancient fishes had not found a way to adapt to life out of the water, we humans would not exist.To investigate this event we can look at the fossil record, but that only tells us about changes in the skeleton.The equally important changes that must have occurred in the soft anatomy and physiology would appear to be lost, undocumented, in the mists of time.Or are they? rnIn two linked papers published this week in Cell, Wang et al.(2021) and Bi et al.(2021) presented a tour-de-force of comparative genomic analysis that shines a light on all those aspects of the transition that cannot be observed from the fossil record.By placing whole-genome sequences from a range of carefully chosen fishes in a phylogenetic context spanning the fish-tetrapod transition (Figure 1), they are able to show in remarkable detail exactly what happened to the genome and the phenotype during that transition.