of a fluorophore depends on both radiative (i.e. fluorescence) and non-radiative (i.e. quenching, FRET) processes, energy transfer from the donor molecule to the acceptor molecule will decrease the lifetime of the donor. Thus, FRET measurements using FLIM can provide a method to discriminate between the states/environments of the fluorophore. In contrast to intensity-based FRET measurements, the FLIM-based FRET measurements are also insensitive to the concentration of fluorophores and can thus filter out artifacts introduced by variations in the concentration and emission intensity across the sample. See also Phasor approach to fluorescence lifetime and spectral imaging References External links Fluorescence Excited-State Lifetime Imaging Lifetime and spectral analysis tools in ImageJ: http://spechron.com Fluorescence Lifetime Imaging Microscopy Principle of TCSPC FLIM (Becker&Hickl GmbH) Fluorescence techniques Optical microscopy techniques