Confocal imaging of samples stained in MB was done as described elsewhere.3,4 For confocal imaging of DMN-stained samples, the imaging system was modified to allow for the excitation of DMN and detection of DMN fluorescence signal. In particular, a 402-nm diode laser (MicroLaser Systems, Garden Grove, California, USA) was used as the light source. All optical elements were selected to optimize the efficiency of light propagation in the visible spectral range. DMN fluorescence was separated with a dichroic mirror (Chroma, Bellows Falls, Vermont, USA), which reflected wavelengths , and focused by a lens onto a pinhole placed in front of the fluorescence photomultiplier tube (PMT). A 520-nm band-pass filter with an FWHM of 40 nm (Edmund Optics, Barrington, New Jersey, USA) was utilized for DMN fluorescence imaging. Elastically scattered light was deflected by a nonpolarizing beam splitter (MellesGriot, Albuquerque, New Mexico, USA) and focused onto a pinhole in front of the reflectance PMT. We employed a water-immersion objective lens (Olympus, Melville, New Jersey, USA), which provided a field of view, lateral resolution of better than 0.9 μm, and axial resolution of . Power incident on the samples did not exceed 1.3 mW.