Four billion years ago, the infant Earth was a seething cauldron of erupting volcanoes, raining meteors, and hot noxious gases, totally devoid of life. But a relatively short time later - only 100 million to 200 million years - the planet was teeming with primitive organisms. What happened? Now you can find out - in a series of 24 vibrant lectures from a leader of the NASA - supported team studying the origins of life in the universe and also one of the nation's foremost science educators. The lectures take you from path-breaking experiments in the 19th century that proved the molecules of life to be no different from other chemicals, to our increasingly sophisticated modern understanding of just how the chemistry of life works, to the near certainty that the 21st century will see spectacular and unpredictable developments in our understanding of how life began. For all its familiarity, life is an elusive concept that is hard to define, much less explain. These lectures show how scientists are systematically building a picture of the process by which those chemical reactions on the early Earth eventually led to the first appearance of the DNA-protein world that remains the fundamental basis of all life today. And you'll join them as they probe for evidence of life beyond our planet. Crammed with fascinating experiments, surprising results, heated debates, blind alleys, and promising leads, the investigation of life's origins is a mystery story in the truest sense - one in which the clues are slowly adding up but the solution is not yet in hand.