Based on the spontaneous Raman spectra, the spectral region from 2850 to 3150 cm -1 was selected for SRS imaging of RTV and PVPVA. Addi onally, the phosphate buffer signal (primarily water OH stretching) was recorded in this region. SRS spectra were recorded using two different spectral resolu ons: high resolu on with a 6 cm -1 spectral step size and 51 spectral points in total (Figure , le ), and low resolu on with a 45 cm -1 spectral step size with 7 spectral points in total (Figure , right). The first reason for two different se ngs was op miza on of the measurement speed based on requirements of in situ dissolu on imaging: the lower resolu on scan took about 10 seconds, whereas the higher resolu on took about 60 seconds. The second reason was the reduc on of the exposure to the laser illumina on, which effec vely reduces the chance for laser induced photodamage (burning). Faster measurements were used throughout each dissolu on experiment and for the final mepoint an image with the high spectral resolu on was recorded.