Before the Big Bang

One of the world's most celebrated cosmologists presents her breakthrough explanation of our origins in the multiverse.What came before the Big Bang, and what exists outside of the universe it created? Until recently, scientists could only guess at what lay past the edge of spacetime. But as pioneering theoretical physicist Laura Mersini-Houghton explains, today new scientific tools are giving us the ability to peer beyond the limits of our universe and test our theories about what is there.