Lately, the use of ultrafast in-volume laser-based processing of transparent materials has gained ground as a 3D-printing method of functional materials, photonics devices and high-density storage media. In this talk, we discuss the use of wide-field third-harmonic imaging that offers a non-destructive means for investigating and characterizing laser-written in-volume complex structures. Specifically, the method is used for identifying laser-induced modifications and establishing their taxonomy over a large area of a material. Unlike confocal arrangements, its ability to capture both the direct and scattered signal enables the collection of comprehensive information related to the local laser-induced modifications. Its inline nature allows for in situ monitoring of the material's response to various laser exposure conditions. As future prospect, it offers a pathway towards the implementation of closed-loop control algorithms, guaranteeing the accuracy and consistency of the desired modifications.