If stains such as toluidine blue are used, Nissl bodies within the cytoplasm of the cell bodies may become visible, appearing as large dark staining bodies. Nissl bodies do not extend into the axon hillock. Neuropil stains very faintly using toluidine blue. | If stains such as toluidine blue are used, Nissl bodies within the cytoplasm of the cell bodies may become visible, appearing as large dark staining bodies. Nissl bodies do not extend into the axon hillock. Neuropil stains very faintly using toluidine blue. |