A method for performing a Western Blot assay, the method comprising: providing a sample supported on a membrane , the sample comprising a plurality of proteins , the plurality of proteins comprising a plurality of target proteins ; performing a probing process by contacting the sample with a fluorescent resonance energy transfer (FRET) solution and allowing the probing process to proceed for a probing time period, wherein: the probing process produces a plurality of labeled target proteins to which first probes and second probes are bound; the first probes each comprise a donor chromophore , the second probes each comprise an acceptor chromophore , and the donor chromophore and the acceptor chromophore are effective as a donor-acceptor pair for FRET; and the FRET solution comprises the first probes , or the second probes , or both the first probes and the second probes ; and while performing the probing process, measuring the labeled target proteins by: irradiating the membrane with an excitation light to excite the donor chromophores , wherein in each labeled target protein , the excited donor chromophore transfers energy to the acceptor chromophore by FRET and, in response, the labeled target protein emits an emission light ; and measuring an intensity of the emission light . providing a sample supported on a membrane , the sample comprising a plurality of proteins , the plurality of proteins comprising a plurality of target proteins ; performing a probing process by contacting the sample with a fluorescent resonance energy transfer (FRET) solution and allowing the probing process to proceed for a probing time period, wherein: the probing process produces a plurality of labeled target proteins to which first probes and second probes are bound; the first probes each comprise a donor chromophore , the second probes each comprise an acceptor chromophore , and the donor chromophore and the acceptor chromophore are effective as a donor-acceptor pair for FRET; and the FRET solution comprises the first probes , or the second probes , or both the first probes and the second probes ; and the probing process produces a plurality of labeled target proteins to which first probes and second probes are bound; the first probes each comprise a donor chromophore , the second probes each comprise an acceptor chromophore , and the donor chromophore and the acceptor chromophore are effective as a donor-acceptor pair for FRET; and the FRET solution comprises the first probes , or the second probes , or both the first probes and the second probes ; and while performing the probing process, measuring the labeled target proteins by: irradiating the membrane with an excitation light to excite the donor chromophores , wherein in each labeled target protein , the excited donor chromophore transfers energy to the acceptor chromophore by FRET and, in response, the labeled target protein emits an emission light ; and measuring an intensity of the emission light . irradiating the membrane with an excitation light to excite the donor chromophores , wherein in each labeled target protein , the excited donor chromophore transfers energy to the acceptor chromophore by FRET and, in response, the labeled target protein emits an emission light ; and measuring an intensity of the emission light . <EOS>