Methyl Green, also known as Double Green SF, is a basic dye, a green microcrystal or powder with metallic luster, molecular weight 608.78, molecular formula C₂₇H₃₅Cl₄N₃Zn.

Methyl Green Stain is used to stain the nucleus of cells in tissue or cell staining, often used to identify DNA, DNA in the nucleus will be stained blue-green when encountered with Methyl Green, and can also be used for immunofluorescence staining or immunohistochemistry staining, 10 ml of staining solution can be stained 20 samples.