This week, we're chilling out in the world of cryogenics, the science of the super-cold. We'll find out what happens to living tissue when it freezes, and how we can use low temperatures to keep organs, and maybe even one day whole bodies, in suspended animation. We also talk to the company behind an attractive new design of super-efficient fridge that runs on magnetism. In the news we hear how computer gamers have contributed to a breakthrough in HIV, why humans are programmed for overconfidence, and how the nervous system controls the immune system. Plus, we ask, is modern medicine altering the human gene pool?