The advent of gravitational wave astronomy has opened new windows to the universe, enabling observations across multiple wavelengths and diverse astrophysical and cosmological origins. In particular, lensing of gravitational waves offers unique opportunities to probe small-scale matter distributions. Given the spin-2 nature and long wavelengths of gravitational waves, it is essential to account for wave and spin effects beyond the geometric optics approximation. In this talk, I will provide an overview of spin wave optics of lensed gravitational waves, highlighting recent advancements and their potential to deepen our understanding of black holes and the universe.