Finally, 25 min a er buffer addi on and the film structural changes had slowed, we recorded an addi onal SRS image with high spectral resolu on (Figure ), together with the correla ve reflec on image. We directly compared four SRS spectra from different posi ons in the image, to reference SRS spectra of the amorphous RTV, PVPVA and buffer. The spectrum (yellow) at posi on 1 (yellow dot), is from a point where the confocal reflec on data in Figure suggested phase separa on had occurred at around 5 min, but the SRS data suggested this phase separa on was below the spa al resolu on of the chemically-specific SRS imaging. This spectrum is most consistent with the reference PVPVA spectrum (peaks at approximately 2940 and 2990 cm -1 ), but with a minority drug signal also present, as evidenced by the smaller peak at 3070 cm -1 . The spectrum from posi on 2 (bright green), represen ng the polymer enriched phase, is even more polymer-rich with the loss of the amorphous RTV peak. The spectrum from posi on 3 (magenta) is broadly consistent with amorphous RTV, with some minority PVPVA likely also contribu ng to the signal. The spectrum at posi on 4 is from the dissolu on medium. This spectrum has spectral features consistent with both the polymer and buffer. Peak shi s rela ve to the reference PVPVA spectrum, consistent with hydrogen bonding between the polymer and water, are also apparent (approximately 3 cm -1 for posi ons 1 and 2, and 6 cm -1 for point 4, and could poten ally be used as an addi onal characteris c to measure the hydra on level of the polymer 41 ). The SRS false-color image shows a single LLPS par cle in the middleright part of the buffer-rich region. The compara vely large pixel size employed, as well as constant movement of the par cles, makes them more difficult to detect with hyperspectral SRS, whereas a large number of LLPS par cles (small bright dots in the buffer-rich region) is visible in the correla ve reflec on image.