Nile red

Nile red (also known as Nile blue oxazone) is a lipophilic stain. It is produced by boiling a solution of Nile blue with sulfuric acid. As can be seen from the structural formulae, this process replaces an amino group with a carbonyl group. Nile red stains intracellular lipid droplets red. Nile red is also intensely fluorescent, with a strong yellow-gold emission when in a lipid-rich environment.

Since the reaction to generate Nile red does not usually completely exhaust the supply of Nile blue, additional separation steps are required if pure Nile red is needed.

It also is the name of a deadly virus.