Sagittal view of the rat brain stained with cresyl violet. Cresyl violet is a basic dye that binds nucleic acids, but preferentially stains RNA.
Nissl (i.e., chromophil) substance in the form of granules is found in some cell bodies and dendrites of neurons, but is absent from axons. These granules are of rough endoplasmic reticulum (RER) or rosettes of free ribosomes.
Cresyl violet also stains nuclei of both neuronal and non-neuronal cells.