Hoechst stains are part of a family of blue fluorescent dyes used to stain DNA. HOE 32021 is a cell dye for DNA. Hoechst dyes are soluble in water and in organic solvents such as dimethyl formamide or dimethyl sulfoxide. Concentrations can be achieved of up to 10 mg/mL. Aqueous solutions are stable at 2-6°C for at least six months when protected from light. For long-term storage the solutions are instead frozen at ≤-20°C.