Neil deGrasse Tyson examines the origin of life in the universe. He begins by considering some reflections by the astronomer Christiaan Huygens before discussing why life's origin is such a difficult scientific topic. He then looks at the early planet Earth and discusses why there is only one tree of life. He considers extremophiles that have the ability to live in environments that appear hostile to life and examines the theory that microscopic life may have originally come to Earth from outer space.
