In this episode, Michael Mosley shows how existence is a struggle and how, minute by minute, from your first breath to your last, your body performs countless small miracles to keep you alive. It starts with a dramatic water birth, shot in slow motion, before a stunning graphics sequence takes us on a breathtaking journey into the heart. We see how that first, crucial breath leads to a dramatic re-plumbing of your entire circulatory system. Michael meets remarkable people who demonstrate how well the human body adapts to extreme environments: Herbert, a world-champion free-diver, who can hold his breath in the depths of the ocean for up to nine minutes; Wim, the Ice Man, who can swim in glacial lakes so cold they would kill a normal person; and Debbie, who has lived for 10 years on a diet of crisps. And finally we see what happens when your body finally fails; we share the last moments of Gerald, an 84-year-old, as he passes away at home with his family gathered around him.