New methylene blue (also NMB)[clarify] is an organic compound of the thiazine class of heterocycles.

It is classified as an azine dye, and the chromophore is a cation, the anion is often unspecified.

[1] NMB is a staining agent used in diagnostic cytopathology and histopathology, typically for staining immature red blood cells.

[2] It is closely related to methylene blue, an older stain in wide use.

Skin contact or inhalation should be avoided.