Obama celebrates young inventors at science fair

US President Barack Obama prepares to demonstrate a winning entry from high school students Payton Karr (L) and Kiona Elliott (C) from Oakland Park, Florida, while he hosts a White House Science Fair in the East Garden of the White House in Washington, April 22, 2013. The students invented and designed a collapsible, transportable, bicycle-powered emergency water sanitation station. [Photo/Agencies]