3,8-Diamino-6-phenylphenanthridine (DAPP) is a heterocyclic aromatic compound featuring a phenanthridine core substituted with amino groups at the 3 and 8 positions and a phenyl group at the 6 position. It is a derivative of ethidium bromide, a well-known nucleic acid intercalator and fluorescent dye. Its primary and significant application is in life science research as a fluorescent probe for nucleic acids. DAPP binds to DNA and RNA through intercalation, resulting in a substantial enhancement of its fluorescence emission. This property makes it a valuable tool for staining and visualizing nucleic acids in gel electrophoresis, particularly as an alternative to ethidium bromide, with potentially improved sensitivity and lower mutagenicity in some contexts. It is also used in fluorescence-based assays to study DNA structure, dynamics, and protein-DNA interactions. As a chemical entity, it serves as a specialized organic synthesis building block, particularly for constructing complex polycyclic aromatic systems and heterocycles containing multiple amine functionalities, which are of interest in materials and medicinal chemistry.