Zoomed view of a serial block face scanning z-stacks through a wt1b-overexpressing heart at 5 dpf. Serial stacks through a ventricle from a myl7:Gal4;eGFP:UAS:wt1b embryo at 5 dpf. Images were obtained by serial block face scanning electron microscopy. Shown here is a magnification of the myocardium in a region where sarcomeres can be observed. Note the z-lines. Remarkable is the disorganized arrangement of the 181 sarcomeres between adjacent cardiomyocytes. Scale bar, 500 nm.