In 1054 AD, the Chinese recorded the explosion of a star so bright that it lit the sky for three weeks, even during the day. It was the explosion of a dying star that was bigger than our sun. NOVA explores this mysterious explosion that led to the discovery of Crab Nebula.

The advance of medicine depends inevitably on the testing of experimental procedures on human volunteers from either the healthy or the sick. Yet such procedures are often dangerous, and may not be of direct benefit to the subject. NOVA examines how individuals' interests are safeguarded, and asks, under what circumstances experiments should be conducted on children.