A brief overview of some approaches to cosmological gravitational lensing is given. Emphasis is placed on the geometric structure of our past null cone, particularly the wavefront catastrophes imprinted on it by the hierarchical galaxy distribution. We conjecture on the natural fractal-like limit of this imprinting process and give some applications to studies of the Cosmic Microwave Background (CMB). Finally, some of the outstanding problems in observational cosmology are discussed.