Many insects and some mammals use smell as a primary means of communication. NOVA explains how, for example, the entire economy of an ant's nest is organized by smell, and how some moths use smell for population control—an ability we is now beginning to understand.

Most of us spend one-third of our lives in a state of which we understand remarkably little—some people sleep for only a few minutes a night, and function perfectly well, while others declare that eight hours isn't enough. NOVA explores traditional notions about how much sleep we need; looks at effects of the sleeping pill, and, perhaps the most baffling of all aspects of sleep—dreaming.