Last week, Argonne National Laboratory hosted the 18th annual Rube Goldberg Machine Contest, which gathered nine high school teams in a competition to build a series of simples tasks, combining the principles of physics and engineering. By using common objects like marbles and bicycle parts, the students were assigned to build a machine that takes at least 20 steps to hammer a nail. In this photo, members of a Hoffman Estates High School team works on assembling a Toyland-themed Rube Goldberg machine. Check out more photos of the competition's complex and colorful Rube Goldberg machines. | Photo courtesy of Argonne National Laboratory.