Vertebrate heart morphogenesis is a complex process that integrates different structures and cell types compelled to interact by genetic and epigenetic factors. Mistakes at any step from cell-commitment to valve formation will have a major impact on heart morphogenesis leading to congenital heart disease. Avian embryos offer an ideal system to study heart development because the development of the four-chambered avian heart is comparable to that of the four-chambered mammalian heart. The avian embryo is readily amenable for optical accessibility and permits direct observation of the cellular movements comprising heart formation in a warm-blooded experimental system. We use quail because of their small sized eggs, their moderately sized breeding adults, their short generation time, and their transgenic feasibility. The transgenic quails developed in the hosting laboratory expressing fluorescent proteins constitute a new model syste. Bright trangenic quails improve the ability to dynamically image vascular development during embryogenesis.Our proposal aims to study the formation of the heart during the embryonic development of quails with special attention to fate mapping myocardium and endocardium progenitors. We will carry out dynamic imaging, using laser scanning microscopes, to image live transgenic or chimeric quail lines that express fluorescent proteins ubiquitously, in the endocardium and in additional tissues or subcellular structures. Using a high-speed confocal microscope we aim to capture the heartbeat at different z-depths. We can reconstruct the data into a 4D figure allowing us to conclude the impedance action of the heart on the endocardium wall.