Abstract
The ecological and evolutionary success of vertebrates stems in large part from their remarkably diverse organs. Understanding how this organ diversity has arisen has been a long-standing goal. What molecular and developmental changes are responsible for the origin and diversification of vertebrate organs, and what evolutionary forces drove these changes? This Review discusses major leaps in our understanding of the molecular evolution of vertebrate organs made possible by technological advances-that is, whole-genome sequencing, functional and single-cell genomics, and genome editing tools. I summarize how organs and cell types evolve at different rates, and the distinct contributions that some types of molecular change make to organ evolution. Finally, I discuss how new, complex traits evolve-from cells to tissues and organs-and how these innovations have fuelled the diversification of vertebrates.