py·ro·nin 
(pīrə-nĭn) also py·ro·nine (-nēn′)
(pīrə-nĭn) also py·ro·nine (-nēn′)n.
Any of a group of xanthene dyes used as a biological stain, especially to detect or track the presence of RNA by staining it red.
[German Pyronin, originally a trademark.]