Safranin O is a stain frequently utilized in microscopy that appears as dark red to brown crystals at room temperature. According to most sources, safranin O is a mixture of the compounds dimethyl safranin and trimethyl safranin, though some only list the dimethyl compound as a constituent of the stain. Safranin O is most commonly employed for counterstaining nuclei red, but may also be used to stain chromosomes and cell walls. Similar to most substances found in the laboratory, safranin O must be handled with care. The stain can cause both skin and eye irritation, and may be harmful if swallowed, absorbed through the skin, or inhaled. Safranin O is also considered an irritant of mucous membranes and the upper respiratory tract, but is not flammable or explosive under typical laboratory conditions.