The heart is essential for our survival and forms during embryonic development. It begins functioning just 22 days after the human embryo is fertilised, which is necessary to support the continued growth of the embryo. We have a sound understanding of the major anatomical stages of heart development however our knowledge of the genetic and cellular events orchestrating its morphogenesis is incomplete. Focussing primarily on the early stages of heart development, my lab uses the zebrafish model to identify novel genes in cardiac development. We do this by creating mutant animals with cardiac defects, we investigate the mechanisms of how these genes function and, for some of these genes, we translate our findings to the mammalian context. Using this approach, we have uncovered several novel genetic regulators of cardiac development: A regulator of the extracellular matrix is required to correctly pattern the cardiac valves; a component important for endosome recycling is required for cell shape changes in the heart, permitting ballooning of the cardiac chambers; and a new gene of unknown function is required for correct cardiac rhythm. These three mutants identify new molecular regulators of cardiac form and function and demonstrate that there is still much to discover in the genetic regulation of the heart.