A. Example arrangement of data for a three probe (m=3) setup in terms of the linear unmixing equation. Emission spectra data (μ) of a mixture are arranged vertically, stacked by emission wavelength and excitation channel (indicated by color and background highlighting). Each column of the reference matrix is the emission spectra of a probe in isolation, arranged in the same way. B. Example data for three probe setup involving a teal fluorescent protein (mTFPI), a yellow fluorescent protein (mVenus), and their covalent fusion (mTFPI-m Venus). Two excitation channels are used, 430 and 505 nm, and fluorescence emission spectra measured.