In this illustrated book, Stephen Hawking and Leonard Mlodinow present the scientific thinking about mysteries of the universe, in nontechnical language. According to quantum theory, the cosmos does not have just a single existence or history. The authors explain that human beings are the product of quantum fluctuations in the early universe, and show how quantum theory predicts the 'multiverse' - the idea that ours is just one of many universes that appeared spontaneously out of nothing, each with different laws of nature. They conclude with an assessment of M-theory, an explanation of the laws governing the universe.