Remember that photo of a surprised President Obama watching a cannon blast a marshmallow across the room, as the 14-year-old who invented the contraption looks on?
Well, it's that time of year again. The president made his rounds on Tuesday at the fourth annual White House Science Fair, meeting with kid geniuses and checking out their projects and experiments. And that meant showing a lot of interest. Here are several photos from the day.
Obama took a look at a 3-D model of the influenza virus as he talks with Eric Chen of San Diego.
He also held up Peyton Robertson's "sandless sand bags" project.
Obama spoke wtih members of a Girl Scout Brownie troop from Tulsa, Okla., about their design for a flood-proof bridge.
And he watched as 13-year-old Gerry McManus, of Hudson, Mass., demonstrated the use of his basketball catapult.
The president tried it out himself.
Obama checked out a robotics display from Chicago students John Moore and Lydia Wolfe.
He met with New York student Elana Simon, who is researching liver cancer.
And talked with Deidre Carrillo, a student from San Antonio, about an electric car.