The 2% aqueous methylene blue solution is a staining solution widely used in histology, microbiology and other fields of life science. Methylene blue is a heterocyclic aromatic dye that is also used as a redox indicator and antioxidant. In a 2% aqueous solution, the concentration of the dye is higher than in lower concentration solutions, which can result in more intense staining.

In histology, methylene blue is often used as a contrast dye to highlight cell structures, especially nuclei, in tissue sections. It is also used in cytology to stain smear preparations of cells to facilitate the recognition and analysis of cell morphology and structure.

In microbiology, methylene blue is used as a simple dye to stain bacteria to make them visible under the light microscope. The staining occurs when the dye attaches to specific structures of the bacteria, such as the cell wall or cell membrane.

The 2% aqueous methylene blue solution can also be used in other scientific applications, such as in aquaristics to treat fungal infections in fish, or in electrochemistry as a redox indicator.

Overall, the 2% aqueous methylene blue solution is a versatile staining agent used in various life science disciplines for staining and visualization of biological samples. The higher concentration of the dye allows for more intense staining, which can be beneficial for certain applications.