Bullying is commonplace in schools, but in recent years cyber-bullying, suicides, and school shootings have shown bullying to be a very serious issue. On this week’s Please Explain we’ll find out what constitutes bullying and aggression among children (and adults), its repercussions, and how parents, children, and schools should address it. We’re joined by Elizabeth Englander, Professor of Psychology and Director of the Massachusetts Aggression Reduction Center at Bridgewater State University, and Jessie Klein, Assistant Professor of Sociology and Criminal Justice at Adelphi University, and author of The Bully Society: School Shootings and the Crisis of Bullying in America’s Schools.

Please Explain is all about the anti-anxiety medications benzodiazepenes. Psychologist Dr. Douglas Mennin and Lisa Miller, contributing editor at New York magazine, whose article “Listening to Xanax” appears in the March 26 issue of the magazine, explain how they work and why they’re addictive.

Barb Stuckey, professional food developer and author of Taste What You're Missing: The Passionate Eater's Guide to Why Good Food Tastes Good, explains the science of taste, and shows how our individual biology, genetics, and brain create a personal experience of everything we taste.

Please Explain is all about the Norovirus, which is the leading cause of outbreaks of food-borne illness. We'll speak with Dr. Aaron Margolin and Dr. Christine Moe.

This week’s Please Explain takes a look at something familiar (yet still mysterious) to every New Yorker: the subway. John Tauranac, architecural historian and designer of city and transit maps, and Andrew Sparberg, former Long Island Railroad manager and director of the railroad technology program at Technical Career Insitutes, talk about how the subway was built and how it transformed the metropolitan area.

This week's Please Explain is the final installment of our series How to Save the World. Jeffrey Sachs discusses whether it's possible to achieve world peace. He's Director of The Earth Institute at Columbia University and Special Advisor to United Nations Secretary-General Ban Ki-moon. His most recent book is The Price of Civilization.

This week's Please Explain continues our series How to Save the World. Glenn Denning, Director, Center on Globalization and Sustainable Development at the Earth Institute at Columbia University, and J. Matthew Roney, Research Associate, Earth Policy Institute, examine the global food supply.

Wherever humans go, they leave trash behind. The average American throws away over 1,130 pounds of waste per year. On this week’s Please Explain, we continue our series How to Save the World, looking at how we dispose of garbage, how recycling and composting and smaller packaging can cut down on the amount of garbage people throw away around the world, and how garbage can be used as a renewable, green energy source. Joining us are Nickolas J. Themelis, Director, Earth Engineering Center, and professor in the School of Engineering at Columbia University, and Elizabeth Royte, author of Garbage Land and Bottlemania.

This week’s Please Explain, the third in our series How to Save the World, is about climate change and how to stop it. David Archer, professor of geophysical sciences at the University of Chicago, and author of The Long Thaw: How Humans are Changing the Next 100,000 Years of the Earth’s Climate, and Global Warming: Understanding the Forecast; and Klaus Lackner, Director of the Lenfest Center for Sustainable Energy at Columbia University’s Earth Institute join us to talk about carbon in the atmosphere, how and why it is causing climate change, and how to slow or stop climate change by using sustainable energy and carbon sequestration.

This week's Please Explains is the second in our series on how to save the world—ways to approach complex global problems such as climate change, food supply, garbage disposal, the global water supply, and violence. Today we're looking at the population explosion—there are now 7 billion people on the planet. We're joined by Hania Zlotnik, director of the population Division at the Department of Economics and Social Affairs at the United Nations, and Dr.Joel E. Cohen, mathematical biologist and the head of the Laboratory of Populations at Rockefeller University and Columbia University, and author of How Many People Can the Earth Support?

We're kicking off a series of Please Explains on how to save the world—ways to approach complex global problems such as climate change, food supply, garbage disposal, population control, and violence. Today's topic is how to protect the world's water supply. Upmanu Lall, Director of the Columbia Water Center, and Sandra Postel, founder of the Global Water Policy Project and National Geographic Freshwater Fellow join us to discuss the state of fresh water around the globe.

Tuberculosis remains one of the world’s deadliest diseases—accounting for 9.4 million cases and 1.7 million deaths in 2009, according to the WHO. Maryn McKenna, science journalist and author of Superbug, and Dr. Neil Schluger, Professor of Medicine, Epidemiology, and Environmental Health Sciences at Columbia University Medical Center and Chief Scientific Officer for the World Lung Foundation, give us a history of the disease, how it spreads, why it’s so hard to treat, and how drug-resistant TB has emerged and what it means for the future of treating the deadly disease.

Almost everyone has closets full of stuff, favorite mementos, and expanding collections of books or shoes or spices or hotel shampoos. But sometimes our emotional attachments to stuff can spiral out of control, and people become not just pack rats but compulsive hoarders. Dr. Robin Zasio, therapist who specializes in treating hoarding and other anxiety-related disorders, explains what compulsive hoarding is and how to treat it. She’ll also give advice about how to live a less-cluttered, better-organized life. She’s the author of The Hoarder in You: How to Live a Happier, Healthier, Uncluttered Life.

New York Times science writer John Tierney , co-author of Willpower: Rediscovering the Greatest Human Strength, talks about self-control. He's joined by Dr. Walter Mischel, Niven Professor of Humane Letters in Psychology, Columbia University. They'll explain how to build willpower and how conserve it for crucial moments.

In October, neuroscientists Sandra Aamodt and Sam Wang were on Please Explain to discuss how a young children’s brains develop. And this week they return to discuss the brains of adolescents and teenagers—from sleep problems, gender differences, behavior issues, learning disabilities, and hormones. They investigate myths about brain development and sort through the factors that matter—and those that don’t—in brain development from childhood to college. They’re the co-authors of Welcome to Your Child's Brain: How the Mind Grows from Conception to College.

How well do you know your child's brain? Take this quiz!

Railroad historian John Hankey, and Bob Lettenberger, Director of Education for the National Railroad Museum talk about the history and significance of the freight and passenger railroads in the United States. They’ll also discuss the deterioration of our passenger railways in the 1950s and 1960s and the current state of rail travel here, compared to other countries.

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Kenneth T. Jackson, Jacques Barzun Professor in History and the Social Sciences at Columbia University, and Lisa Keller, Associate Professor of History at SUNY Purchase, both editors of The Encyclopedia of New York City, second edition, explain who the people behind the names of familiar tunnels, bridges, and expressways are. From the Van Wyck, the Major Deegan, and the Bruckner to the Kosciusco Bridge, the Holland Tunnel to Tompkins Square Park, Washington Heights, and Astoria.

Herman Cain has gotten a lot of attention for his 9-9-9 tax plan, Governor Rick Perry recently unveiled his own flat tax proposal, and there have been numerous presidential candidates who have made a flat tax plan the basis of their campaigns. Joseph J. Thorndike is the director of the Tax History Project at Tax Analysts and a contributing editor for Tax Notes magazine looks at the history of the flat tax, how it compares to our current tax system, and what the proposed flat tax plans would mean for the U.S. economy.

Anahad O’Connor, columnist for the New York Times Well blog and author of Always Follow the Elephants and Never Shower in a Thunderstorm, and Dr. Rachel Vreeman, co-author of Don’t Swallow Your Gum and Don’t Cross Your Eyes...They'll Get Stuck That Way, and assistant professor of pediatrics at Indiana University, and talk about medical myths and wives tales—adages like “starve a fever, feed a cold” and that caffeine will stunt your growth. They’ll explain where they came from and why they persist and they’ll, as well as which are right and which are wrong.

Lizzie Post and Anna Post (great-great granddaughters of Emily Post) explain the ins and outs, the rules and pointers of communicating by e-mail and online. They are co-authors of the 18th edition of Emily Post’s Etiquette.