Are we alone in the universe? Astronomer Dimitar Sasselov is leading the hunt for "super-Earths" -- rocky planets like our own that orbit other stars. He and his colleagues believe it's only a matter of time before they discover a super-Earth that is not only habitable, but home to some form of life. He explains that the search for extraterrestrial life takes to forms: planet hunting, and the creation of the world's first artificial cells.