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President Barack Obama talks with Elana Simon, 18, of New York City, about her cancer research project that is part of the 2014 White House Science Fair exhibit on display in the State Dining Room of the White House in Washington, Tuesday, May 27, 2014. Simon, at age 12, was diagnosed with fibrolamellar hepatocellular carcinoma, a little-known form of cancer that affects the liver. After surviving the disease, she now helps scientists research the genetics behind it. Obama was celebrating the student winners of a broad range of science, technology, engineering and math (STEM) competitions from across the country. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama tosses a basketball as he tours the 2014 White House Science Fair exhibits that are on display in the State Dining Room at the White House in Washington, Tuesday, May 27, 2014. Students from Hudson, Mass., showed Obama their basketball catapult. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama speaks with some of the 2014 White House Science Fair kids behind him, Tuesday, May 27, 2014, in the East Room of the White House in Washington. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama stands with John Moore, 19, center, and Lydia Wolfe, 18, right, both of Chicago, as he looks over a robot during a tour of the 2014 White House Science Fair exhibits that are on display in the State Dining Room at the White House in Washington, Tuesday, May 27, 2014. (AP Photo/Susan Walsh) ( Obama Science )

Josh Troutman of Bismark, N.D., left, and Tanner Schantz, of Bismark, N.D., show off their vision of the city of the future during the 2014 White House Science Fair, Tuesday, May 27, 2014, at the White House in Washington. (AP Photo/ Evan Vucci) ( Obama Science )

President Barack Obama speaks in the East Room of the White House in Washington, Tuesday, May 27, 2014, during the 2014 White House Science Fair. (AP Photo/ Evan Vucci) ( Obama Science )

President Barack Obama smiles as he speaks in the East Room of the White House in Washington, Tuesday, May 27, 2014, during the 2014 White House Science Fair. (AP Photo/ Evan Vucci) ( Obama Science )

U.S. President Barack Obama (L) speaks with Avery Dodson, Natalie Hurley, Miriam Schaffer, Claire Winton and Lucy Claire Sharp, winners of the Junior FIRST Lego League Challenge, with the "Flood-proof" bridge design project during the 2014 White House Science Fair at the White House May 27, 2014 in Washington, DC. Obama hosted the science fair to announce new steps as part of his Educate to Innovate campaign, and celebrated student winners of a range of science, technology, engineering and math (STEM) competitions from across the country. (Photo by Aude Guerruccip-Pool/Getty Images) ( 494047675 )

U.S. President Barack (L) Obama catches a ball from the "Basketball Catapult" a science project of Brooke Bohn (R), Daisjaughn Bass and Gerry McManus from Hudson Massachusetts, winners of the Raytheon and NE Patriots Science of Sports during the 2014 White House Science Fair at the White House, May 27, 2014 in Washington, DC. (Photo by Aude Guerruccip-Pool/Getty Images) ( 494047679 )

U.S. President Barack Obama (R) speaks with Deidre Carrillo, winner of the Electrathon and NCWIT Aspiration in Computing for her electric car project during the 2014 White House Science Fair at the White House, May 27, 2014 in Washington, DC. (Photo by Aude Guerruccip-Pool/Getty Images) ( 494047683 )

U.S. President Barack Obama (L) looks at the First Robot project of John Moore (C) and Lydia Wolfe of Chicago, Illinois, during the 2014 White House Science Fair at the White House, May 27, 2014 in Washington, DC. (Photo by Aude Guerruccip-Pool/Getty Images) ( 494050813 )

U.S. President Barack Obama looks at the Cancer Research project of Elena Simon, New York City during the 2014 White House Science Fair at the White House, May 27, 2014 in Washington, DC. (Photo by Aude Guerruccip-Pool/Getty Images) ( 494050819 )

Maria Hanes, 19, of Santa Cruz, Calif., left, and President Barack Obama, right, watch as two cushioned helmets bump together as Obama toured the 2014 White House Science Fair exhibits that are on display in the State Dining Room of the White House in Washington, Tuesday, May 27, 2014. Hanes was explaining how she developed a concussion cushion football helmet. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama poses for a photo with Karen Fan, 17, left, and Felege Gebru, 18, both of Newton, Mass., as the president toured the 2014 White House Science Fair exhibits that are on display in the State Dining Room of the White House in Washington, Tuesday, May 27, 2014.Gebru and Fan showed Obama their pedestrian crossing signal. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama shakes hands in the East Room of the White House in Washington, Tuesday, May 27, 2014, during the 2014 White House Science Fair. (AP Photo/ Evan Vucci) ( Obama Science )

Nicolas Badila of Jonesboro, Ga., tells President Barack Obama how to play STEMville, a STEM video game, as Obama toured the 2014 White House Science Fair exhibits that are on display in the State Dining Room at the White House in Washington, Tuesday, May 27, 2014. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama smiles as he speaks in the East Room of the White House in Washington, Tuesday, May 27, 2014, during the 2014 White House Science Fair. (AP Photo/ Evan Vucci) ( Obama Science )

President Barack Obama talks with Peyton Robertson, 12, of Ft. Lauderdale, Fla., about how his sandless sandbags work while touring the 2014 White House Science Fair exhibits on display in the State Dining Room of the White House in Washington, Tuesday, May 27, 2014. Robertson designed a new kind of sandbag to protect against flooding from hurricanes and other disasters. Obama was celebrating the student winners of a broad range of science, technology, engineering and math (STEM) competitions from across the country. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama poses for a photo with students from Los Fresnon, Texas, as Obama tours the 2014 White House Science Fair exhibits that are on display in the State Dining Room of the White House in Washington, Tuesday, May 27, 2014. The students developed an app to help a visually-impaired student navigate their school. (AP Photo/Susan Walsh) ( Obama Science )

President Barack Obama tries to catch a basketball as Gerry McManus, 13, of Hudson, Mass., watches, during a tour of the 2014 White House Science Fair exhibits that are on display in the State Dining Room at the White House in Washington, Tuesday, May 27, 2014. McManus and two other students showed Obama their basketball catapult. (AP Photo/Susan Walsh) ( Obama Science )

Parker Owen, of Columbiana, Ala., demonstrates his "Cycle-Leg" during the 2014 White House Science Fair, Tuesday, May 27, 2014, in Washington. President Obama invited students to the White House to celebrate the student winners of a broad range of science, technology, engineering and math (STEM) competitions from across the country. (AP Photo/ Evan Vucci) ( Obama Science )

President Barack Obama stands with, from left, Gerry McManus, 13, Daisjaughn Bass, 13, and Brooke Bohn, 14, all of Hudson, Mass., as he tours the 2014 White House Science Fair exhibits that are on display in the State Dining Room at the White House in Washington, Tuesday, May 27, 2014. The students showed Obama their basketball catapult. (AP Photo/Susan Walsh) ( Obama Science )

Peyton Robertson, 12, of Ft. Lauderdale, Fla., shows off his "sandless" sandbag during the 2014 White House Science Fair, Tuesday, May 27, 2014, at the White Housein Washington. (AP Photo/ Evan Vucci) ( Obama Science )

US President Barack Obama (R) holds up a 3-D model of the influenza virus as he talks with Eric Chen, of San Diego, California, during the White House Science Fair at the White House in Washington, DC, May 27, 2014.The White House Science Fair celebrates the student winners of a broad range of science, technology, engineering and math (STEM) competitions from across the country. AFP PHOTO / Jim WATSON/AFP/Getty Images ( 530170413 )

US President Barack Obama (L) talks with a Girl Scout Brownie troop from Tulsa, Oklahoma about their design for a "flood proof" bridge, during the White House Science Fair at the White House in Washington, DC, May 27, 2014. The White House Science Fair celebrates the student winners of a broad range of science, technology, engineering and math (STEM) competitions from across the country. AFP PHOTO / Jim WATSON/AFP/Getty Images ( 530170733 )