Excitation at 405 nm specifically detects J-aggregates in the mitochondria. (a) HeLa cells were stained with 2.5 μM JC-1 (15 min, RT). Cells were excited at 405 or 488 nm and imaged by an upright Leica SPE confocal microscope (Leica, Wetzlar, Germany) ( × 40 water deep lens), using a single spectral detector. Emission spectra ranging from 513–641 nm in 10 nm intervals are depicted. (b) HeLa cells were grown in 35 mm glass-bottom dishes and stained with JC-1 (see a). Cells were imaged by Zeiss LSM 510 META confocal microscope (Carl Zeiss, Jena, Germany) using × 63 lens and the 405, 488 and 561 nm lasers. Filters used: BP 505-550 for the green channel and BP 575-630 for the red channel.