Telescopes act as natural time machines: looking out in space amounts to looking back in time. Gravitational lensing helps us see farther by making distant galaxies appear bigger and brighter. We can detect galaxies that would otherwise be too faint and probe structures that would otherwise be unresolved. The key is discovering good gravitational lens systems and understanding how they distort our view of the background galaxies. Combining observations, theory, and computation lets us find and focus powerful "cosmic telescopes" that enhance our ability to study the young universe.