Last year, DARPA granted aerospace firm, Aeronvironment, a chunk of change and six-months to demonstrate a bird-sized Nano Air Vehicle (NAV). This video shows the result: the "smallest ever free-flying aircraft to hover and climb with flapping wings."

The Pentagon's wacky sci-fi department DARPA has been working on robotic hummingbird-based drones to serve as miniature spies. They're not nearly as agile or adorable as real hummingbirds, but DARPA is well on their way to achieving that dream.

AreoVironment is building the world's smallest UAV, called the Nano Air Vehicle, that has moving wings instead of a propeller or engine. DARPA has given the company $636,000 and six months to demonstrate an ultra-small UAV that will be under three inches long and under 10 grams.