In vivo imaging of brainstem slices. Detection of non-recombined and recombined cells in a living brainstem slice from a reporter mouse crossed with an Egr2Cre/+ driver line. A) Red fluorescence, B) green fluorescence, C) merged picture. The green fluorescence demonstrates successful detection of recombined cells in vivo. Red cells represent non-recombined cells (arrow). Scale bar is 50 μm.