Figure 4. Comparison of the inner and outer nuclear layers of the retina. A: Without a fluorescent nuclear dye (ethidium bromide homodimer; EthD-1) counterstain. B: With nuclear fluorescent dye. Panels A and B show the inner nuclear layer imaged with third harmonic generation (THG) and two-photon autofluorescence (TPAF). The EthD-1 nuclear staining (Panel B, x), coincides with the THG signal from the cell nuclei (Panel A, *). C: An adjacent histological section stained with hematoxylin and eosin. Scale bar=20 µm.