This chapter examines the developmental mechanisms underlying evolutionary novelties. It first considers the role of the environment in evolutionary innovations, with particular emphasis on how environmental perturbations result in the release of cryptic genetic variation. It then explores where the positional information for novel characters comes from before explaining derived mechanical stimuli and the origin of novelties in the avian hind limb skeleton. It also discusses the origin of character identity networks and the evolution of novel signaling centers, focusing on two novel morphological characters: the butterfly eyespot and the turtle carapace. Finally, it reflects on the developmental biology of novelties, emphasizing the complex and multifaceted nature of the evolutionary changes in the developmental mechanisms that contribute to the origin of novel body parts.