Comparison of the novel dye STAR635P (a) and the benchmark dye Atto647N. (b) The tubulin cytoskeleton was immunolabeled in fixed PtK2 cells and imaging of the same area in the cell performed in the confocal and STED modes. Note the absence of virtually any background with the STAR635P staining. Images display raw data. Imaging was performed using a beam scanning STED microscope equipped with a Ti:Sapphire laser.