Micro-submarine. Conceptual colored scanning electron micrograph (SEM) of a micro-submarine (blue/gray) in a human artery. This tiny submarine was made by computer-guided lasers. Laser light caused an acrylic liquid to polymerize, building up the submarine in layers 10 micrometers thick. Tiny nanorobots such as this could be used for detecting and repairing defects in the human body. Powered by a small propeller, they could travel to sites of blockage or damage in blood vessels and repair them from within, restoring correct blood flow. This submarine was made by microTEC of Duisberg, Germany.