Alien Empire Pearl, 8.30pm Miniature lenses and cameras, endoscopes and straightscopes are used to shrink viewers down and take them on a journey into the world of insects, allowing a close-up view of their world as never seen before. Trial And Error Pearl, 9.30pm Gene therapy is a beautifully simple concept. For any disease caused by a genetic mutation you remove the defective genes and replace them with healthy ones. But scientists need to discover how to get the healthy genes into the patient's cells. This programme tells the story of the Gelsinger family, whose son Jesse died while taking part in a gene therapy trial.