U.S. President Obama speaks to the national winners as he hosts a White House Science Fair in the East Room at the White House in Washington

 
U.S. President Obama speaks to the national winners as he hosts a White House Science Fair in the East Room at the White House in Washington
U.S. President Barack Obama speaks to the national winners as he hosts a White House Science Fair in the East Room at the White House in Washington, April 22, 2013. REUTERS/Larry Downing