Immunofluorescence photomicrographs of differentiated stem cells embedded in hydrogel in vitro (A,B) and in vivo (C, D), expressing green fluorescence protein (GFP, green), βIII tubulin (BIII, red) and counterstained with the nuclear marker DAPI (blue). In vitro preparations (A,B) illustrate the variable expression of GFP within this cell line (low expression, arrowheads; high expression, arrows). Low magnification image in (C) showing location of stem cells in the cochlea, and higher magnification of inset in (D) showing immunopositive labeling. Scale bars = 20 μm (A,B,D); 50 μm (C).