Word of the day

Eosin – a red fluorescent dye C₂₀H₈Br₄O₅ obtained by the action of bromine on fluorescein and used especially in cosmetics and as a toner; a red to brown sodium or potassium salt used especially as a biological stain for cytoplasmic structures; fluorescent acidic compounds which bind to and form salts with basic, or eosinophilic, compounds like proteins containing amino acid residues such as arginine and lysine, and stains them dark red or pink as a result of the actions of bromine on eosin.