For Percival Zhang, growing up in China meant learning to appreciate just how critical a stable food supply is to avoiding social unrest and disasters like famine.
When he became an associate professor of biological systems engineering at Virginia Tech, he got to thinking just how risky growing food has become because of the finite resources it requires: land, water, seeds and fertilizer.
Plenty of other plants on Earth, on the other hand, aren't so demanding.
For the last five years, graduation day has been as much a time for apprehension as for celebration.
Even now, with the Great Recession over, many recent graduates are still struggling to turn their high school and college diplomas into tickets for a better life. The unemployment rate for Americans under age 25 remains more than double the overall rate of 7.5 percent.
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The Whitehouse has announced that President Obama's National Security Advisor is resigning and he will be replaced by Susan Rice, the U.S. Ambassador to the United Nations. NPR's Ron Elving is here to tell us more. Ron, some months ago, Ms. Rice was rumored to be nominated Secretary of State - that, of course, did not happen. So why don't you give us a quick fill on the back story.