Much of the phenotypic diversity present in animals is established in the early embryo by the process of pattern formation. To date, research has mostly focused on the role played by gene regulatory networks (GRNs) in shaping this process. However, it is becoming increasingly apparent that GRNs alone seldom explain pattern formation or its evolvability, and that the evolution of animal form is not reducible to the evolution of genes, or even gene networks. In my lab we take a multi-scale integrative approach, combining mathematical models, experimental embryology and microscopy to study the mechanisms underpinning the emergence and evolution of phenotypes. In particular, we compare posterior development in zebrafish and two species of Lake Malawi cichlids: Astatotilapia calliptera and Rhamphochromis chilingali, which exhibit vast morphological diversity with practically identical genomes.