Representative confocal images of early postnatal development tissue sections P2 (A) and P7 (B, C) respectively, showing native fluorescence of AzG (green, A’”, B”), mKO (red, A”-C”), and immunolabeling for cKit (cyan, A”, B’”, C’”), pHH3 (magenta, A”‘-C”‘), sytox (white, A”“-C”“) and tropomyosin (blue, A”“-C”“), scale bar 50μm in A, B, C; 10μm in A’-C’. Yellow arrow shows cKit+/AzG+/pHH3+ amplifying cardiac progenitor in P2 cardiac sections (A), and AzG+/cTnl+ immature cardiomyocyte in P7 section (C).