Unstained (A) and DCX— immunostained (B) E12.5 fixed tissue sections were treated with either fresh or reused TrueBlack as indicated for 3 minutes, and olfactory epithelia (OE) were imaged. Arrows indicate autofluorescent red blood cells, which are present in untreated tissue, but greatly reduced by treatment with fresh TrueBlack. With more reuse, TrueBlack gradually lost its ability to decrease red blood cell autofluorescence, and by the 8th use induced background fluorescence (asterisk).