U.S. President Barack Obama reacts as Joey Hudy of Phoenix, Arizona launches a marshmallow from his Extreme Marshmallow Cannon in the State Dining Room of the White House during the second White House Science Fair in Washington February 7, 2012. The fair celebrates the achievements of student winners of a broad range of science, technology, engineering and math (STEM) competitions from across the country. (Xinhua/AFP Photo)
