The ELF™ 97 Endogenous Phosphatase Kit can be used to detect phosphatase activity with the ELF™ 97 phosphatase substrate that upon hydrolysis produces a bright and photostable yellow-green fluorescent precipitate at the site of enzymatic activity. This fluorescent precipitate has several unique spectral characteristics, including an extremely large Stokes shift, 180 nm that makes it easily distinguishable from endogenous fluorescence.