Evolutionary developmental biology (“Evo-Devo”) emerged 30 years ago thanks to the continuous progress of molecular biology. At first conceptually disconnected from the questions raised by the synthetic theory of evolution, Evo-Devo gradually took a prominent role in the making of a “new synthesis”. Embryogenesis is controlled mainly by two categories of genes: selector genes that directly regulate other genes activities in precise spatial patterns, and signalling genes that inform continuously the embryonic cells on their precise spatial position. Many of these gene functions are strikingly conserved across animal phyla and studying these functions provides precious information on the evolution of body plans. Most often, the same genes are reused for different functions at various developmental times. Recent studies on the genetic specification of naturally selected variants illustrate this versatility as involved genes are all multifunctional developmental factors. The paradigm of gene regulation networks helps to explain both the robustness of embryonic development and its “evolvability,” since regulatory relations between selector genes are encoded in numerous short regulatory DNA fragments that are susceptible to gradual modifications – as postulated long ago by the modern synthesis.