Abstract: Provided herein are methods for classifying or characterizing a biological sample in vivo or ex vivo in real-time using time-resolved spectroscopy and/or electrical stimulation. A biological sample may produce a responsive fluorescence signal when irradiated by a light excitation signal or pulse at a predetermined wavelength. The responsive fluorescence signal may be recorded. The intensity of the excitation wavelength may be recorded and used to normalize the recorded responsive fluorescence signal. The biological sample may produce a responsive electrical signal in response to electrical stimulation. Raw fluorescence decay data may be generated from the responsive fluorescence signal and pre-processed. The pre-processed raw fluorescence decay data may be de-convolved to remove an instrument response function therefrom and generate true fluorescence decay data.