Martius Yellow 0.5% is a solution used in histology to selectively stain specific cell structures and tissue components. The dye Martius Yellow is a synthetic azo dye derivative characterized by its yellow color. The 0.5% solution allows sufficient concentration of the dye to stain effectively while providing precise control over the staining process.

Martius Yellow is often used in combination with other dyes to stain multiple tissue components simultaneously to facilitate microscopic analysis. For example, it is often used with fuchsin and crystal violet in what is known as Martius yellow-fuchsin-crystal violet staining to differentially stain connective tissue, cell nuclei and cytoplasm. In this combination, Martius yellow stains connective tissue fibers yellow, while fuchsin stains elastic fibers red and crystal violet stains cell nuclei purple.

Because Martius yellow is used in combination with other dyes, it is important to carefully monitor and control the staining process to achieve optimal results. The 0.5% solution allows precise adjustment of the dye concentration to achieve accurate and effective dyeing.