When did the Universe form its first galaxies? What do galaxies look like at the epoch when the Universe formed most of its stars? Some of the answers to those questions (and others) await a new generation of large ground and space based telescopes. In the meanwhile, strong gravitational lensing has become a useful tool to boost the power of present day telescopes, enabling detailed studies of galaxies that are otherwise either too dim or have too small of an angular size on the sky. In this talk, I will present applications of strong gravitational lensing using galaxy clusters as cosmic telescopes. I will highlight some exciting recent results from my team, and conclude with future prospects.