Safranin O kit is used for visualizing and staining of cartilage, mucins and mastocytes in formalin fixed and paraffin mounted tissue samples, but also in frozen tissue sections. It contains Safranin O dye, used in histology and cytology as red nuclear counterstain. Safranin O dye is often used for detecting chondrocytes originating from human and rodent mesenchymal stem cells. Fast Green F.C.F. dye stains background structures, creating a clear and visually rich contrast. Optionally, ErioGnost reagent can be used to achieve selective nuclear staining with a darker hue than with using Safranin O reagent.