There are provided a wavelength selective absorption filter including a resin, and four types of dyes A to D each having a main absorption wavelength range in different specific wavelength regions, in which an absorbance Ab () of the wavelength selective absorption filter at a wavelength nm satisfies specific Relational Expressions (I) to (VI), and an organic electroluminescent display device.

There are provided a wavelength selective absorption filter including a resin, and four types of dyes A to D each having a main absorption wavelength range in different specific wavelength regions, in which an absorbance Ab () of the wavelength selective absorption filter at a wavelength nm satisfies specific Relational Expressions (I) to (VI), and an organic electroluminescent display device.

Disclosed are: a fluorescent compound represented by general formula (I), (I), or (I), as a fluorescent compound which has high retention in a lipid bilayer, has excellent ease of handling, and can achieve uniform dyeing in a dyeing target; and a lipid bilayer dyeing method and an endocytosis detection method using said compound.

##STR00001## Ch is a hydrophobic-field-sensitive fluorescent chromophore in which the fluorescence intensity increases in hydrophobic environments; A-H is an anionic functional group capable of generating anions by deprotonation; X.sup.n+ is a positive ion having biological compatibility; n is 1, 2, or 3; L is a linker that binds to a hydrophobic-field-sensitive fluorescent chromophore and links the fluorescent chromophore and the anionic functional group; and LH.sup.+ indicates a state wherein the linker, which contains a cationic functional group capable of generating cations by protonation, has generated a cation by protonation.

Disclosed are: a fluorescent compound represented by general formula (I), (I), or (I), as a fluorescent compound which has high retention in a lipid bilayer, has excellent ease of handling, and can achieve uniform dyeing in a dyeing target; and a lipid bilayer dyeing method and an endocytosis detection method using said compound.

##STR00001## Ch is a hydrophobic-field-sensitive fluorescent chromophore in which the fluorescence intensity increases in hydrophobic environments; A-H is an anionic functional group capable of generating anions by deprotonation; X.sup.n+ is a positive ion having biological compatibility; n is 1, 2, or 3; L is a linker that binds to a hydrophobic-field-sensitive fluorescent chromophore and links the fluorescent chromophore and the anionic functional group; and LH.sup.+ indicates a state wherein the linker, which contains a cationic functional group capable of generating cations by protonation, has generated a cation by protonation.