Methylene Blue 0.03%, aqueous is a single solution used in various fields, including histology, in scientific laboratories and as an in vitro diagnostic agent. In histology, it is used to stain cell structures and to examine tissue samples. In scientific laboratories, the solution is used to examine cell structures and identify live and dead cells. As an in vitro diagnostic agent, it is used to examine cell structures and to visualize pathological changes in tissue samples.

It is an aqueous solution of methylene blue (C.I.: 52015), with the formula C16H18N3SCl. Methylene blue is a heterocyclic aromatic amine. The solution has a blue color and is generally stable when stored at room temperature.

Methylene Blue 0.03%, aqueous interacts with cell structures and forms an electrostatic compound that results in the staining of cells. The solution has the ability to distinguish live and dead cells as it is reduced only in dead cells.