Non-linear op cal (NLO) imaging techniques, such as s mulated Raman sca ering (SRS) and coherent an -Stokes Raman sca ering (CARS) microscopy, are more advanced Raman-based imaging techniques that excel in rapid three-dimensional visualiza on of chemical and structural distribu ons of a sample at a submicrometer level of detail. Sum frequency genera on (SFG), on the other hand, can complement coherent Raman microscopy by classifying any bulk structures as non-centrosymmetric crystals or amorphous/centrosymmetric crystals . The advent of modern NLO microscopy occurred in 1999 with the demonstra on of Zumbusch et al of CARS microscopy 15 , followed by a demonstra on of SRS microscopy by Freudiger et al in 2008 . In the last decade, SRS microscopy has become increasingly popular due to be er spectral data and simpler user experience, namely the lack on non-resonant background signal and a linear concentra on dependence. CARS microscopy, some mes augmented with SFG, has been used to image the distribu on of API solidstate forms, as well as changes during storage and dissolu on . CARS and SRS have also been used to image API and excipient distribu ons in dosage forms (or intermediates) including tablets , extrudates 19, 23 , films and API-loaded mesoporous silica micropar cles .