Toluidine Blue 0.1% is a common staining solution in biological and medical research and is a dilute solution of the basic dye Toluidine Blue in water. As a thiacinic dye, toluidine blue is used in histology and cytology to stain cell structures such as nuclei and cytoplasm. It stains acidic tissue components, such as nucleic acids, blue and has a high affinity for mast cells, enabling its use in the identification of these cells.

The 0.1% solution of toluidine blue is usually sufficiently dilute to allow clear and differential staining of cells and tissues without compromising detailed identification. Its flexibility allows it to be adapted to the specific needs of a variety of experimental protocols.

In addition, toluidine blue is characterized by its metachromatic properties. These allow differentiated viewing of various cellular structures and components, as the original blue coloration can change to purple or even red upon interaction with certain molecules or tissue structures. Especially in the study of proteoglycans, the metachromasia of toluidine blue proves to be extremely useful, as it allows a clear delineation of these tissue components.