Since the discovery, that a tightly focused femtosecond laser beam can induce a highly localized and permanent refractive index change in a wide range of dielectrics, ultrafast laser inscription has found applications in many elds due to its unique 3D and rapid prototyping capabilities. These ultrafast laser inscribed waveguide devices are compact and lightweight as well as inherently robust since the waveguides are embedded within the bulk material. In this presentation we will review our current understanding of ultrafast laser - glass lattice interactions and its application to the fabrication of inherently stable, compact waveguide lasers and astronomical 3D integrated photonic circuits.