We've been watching those quadrotors quite a long time now, and i tell you, they get cleverer every time. In this video, uploaded by TheDmel, a team of quadrotors autonomously build a cubic structure made of modular parts. It is most impressive how the quadrotors place each piece with precision to place. The pieces use strong permanent magnets to bond each other. Three people work on this project, Quentin Lindsey, Daniel Mellinger, and Vijay Kumar, from the GRASP Lab, University of Pennsylvania.