The 3% methenamine solution is an aqueous solution containing methenamine at a concentration of 3% (weight/volume). Methenamine, also known as hexamethylenetetramine, is an organic compound used in various applications, including as a preservative, disinfectant, and antiseptic.

In histology and microscopy, methenamine is commonly used as a component of methenamine silver stains, such as Gomori methenamine silver stain (GMS) or Jones methenamine silver stain. These staining methods are used to visualize specific structures or microorganisms in tissue samples. For example, GMS staining is used to visualize fungi and certain components of basement membranes, while Jones methenamine silver staining is used to visualize basement membranes and mesangium in kidney biopsies.

When using methen using methenamine solutions in histology, care should be taken to use the proper concentration and recommended protocols to achieve optimal staining results.