Saul Loeb / AFP - Getty Images

U.S. President Barack Obama reacts as 14-year-old Joey Hudy of Phoenix, Ariz. launches a marshmallow from Hudy's "Extreme Marshmallow Cannon" during a tour of the White House Science Fair in the State Dining Room on Feb. 7.

Barack Obama hosted a White House science fair Feb. 7, featuring projects designed by more than 100 students from across the country. The projects included a robot that helps senior citizens connect with their families via Skype, and a portable disaster relief shelter that could be used to house people who have been displaced from their homes.

During his visit to the fair, Obama helped 14-year-old Joey Hudy fire off the Extreme Marshmallow Cannon, one of the Phoenix student's inventions.

"The Secret Service is going to be mad at me about this," Obama joked. Afterward, he told his audience that shooting a marshmallow through the air gun was "very exciting."

Related links:

• Obama calls for more funding to boost science education
• Follow @msnbc_pictures on Twitter

-- The Associated Press contributed to this blog post