Cavity Resonator Integrated Grating Filters (CRIGFs) are a peculiar mix between microcavities and Guided-Mode Resonant Filters (GMRFs). They rely on the coupling of free-space beams to guided and localized modes in a multilayer structure by subwavelength gratings. They provide spectrally selective reflection for tightly focussed beams, combining high Q-factors with high angular and positioning tolerances. Recently, their unusual properties have been harnessed to design and demonstrate compact and robust Extended Cavity Diode Laser (ECDL) with single-mode and narrow-linewidth emission in the near infrared and Extended Cavity Quantum Cascade Laser (ECQCL) with tunable emission in the mid-infrared. More recent work have taken advantage of new geometries on thermo-optic and non-linear material to demonstrate thermal tuning and second harmonic generation at telecom wavelengths. In this contribution, the principle and key features of CRIGFs will be presented together with the applications listed above.