Rose George, author: "The Big Necessity: The Unmentionable World of Human Waste and Why It Matters", Leeds, U.K.
Frank Rijsberman, director of water, sanitation & hygiene, Bill & Melinda Gates Foundation, Seattle, Wash.
Daniel Yeh, associate professor, civil and environmental engineering, University of South Florida, Tampa, Fla.
Jim McHale, vice president, engineering, American Standard Brands, Piscataway, N.J.
Toilets, as most of us know them, haven't changed much since the 1800s—they use a lot of water, and require an infrastructure that many communities can't afford. Ira Flatow and guests look at the problem of access to sanitation, and how engineers are making toilets better.