One of the best tools astronomers have to glimpse the distant universe is a technology that nature invented. Cosmic magnifying glasses called gravitational lenses help scientists zoom in on far-away scenes they could never spot otherwise.
In a recent survey of a section of the universe, researchers counted 67 new gravitational lenses, leading them to believe there are nearly half a million similar lenses in the rest of the universe.
More: http://www.space.com/scienceastronomy/080304-gravitational-lenses.html