The documentary 'The Knowledge of Healing' is an illuminating examination of Tibetan medicine, a practice which has developed over two millennia into a modern day successful method of healing that rivals western medical practices. Unlike Western medicine, based on biochemistry, Tibetan medical thinking (which is strongly rooted in Buddhist principles) views the human body as governed by an elaborately organized system of energies flowing through a network of channels. In the 12th century, the Gyüshi (Knowledge of Healing) was created, a text codifying this intricate system. The medications used comprise herbs, roots, minerals, etc. After flourishing for centuries, most Tibetan medical schools were destroyed by the Chinese in the 1950's and 1960's, and many physicians were executed. Speaking from exile, the Dalai Lama argues for the value of Tibetan medicine, while his personal physician Dr. Tenzin Choedrak describes the principles behind it. We follow physicians in India and Siberia treating patients for a variety of ailments from paralysis to heart disease, and meet researchers in Israel and Switzerland to see how western clinical studies are testing the effectiveness of Tibetan medicine.

Sagan discusses the story of the Heike crab and artificial selection of crabs resembling samurai warriors, as an opening into a larger discussion of evolution through natural selection (and the pitfalls of intelligent design). Among the topics are the development of life on the Cosmic Calendar and the Cambrian explosion; the function of DNA in growth; genetic replication, repairs, and mutation; the common biochemistry of terrestrial organisms; the creation of the molecules of life in the Miller-Urey experiment; and speculation on alien life (such as life in Jupiter's clouds). In the Cosmos Update ten years later, Sagan remarks on RNA also controlling chemical reactions and reproducing itself and the different roles of comets (potentially carrying organic molecules or causing the Cretaceous–Paleogene extinction event).

This episode explores how scientists delved ever deeper into the world of the cell, seeking to reveal the magic ingredient that can spark a bundle of chemicals into life. Their discoveries have brought us to the brink of being able to create life for ourselves.