The most common cell body stain used in brain histology is called

Biological tissue has little inherent contrast in either the light or electron microscope. ... Hematoxylin and eosin (H&E stain) is the most commonly used light microscopical stain in histology and histopathology.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.