It weighs just 80 milligrams, has a pair of wings that flap 120 times a second and has taken 10 years to develop.
The Robobee, inspired by the biology of a fly, is believed to be the first working model of a flying insect.
Harvard University post-graduate student Pakpon Chirarattananon has recorded the first flight of the RoboBee micro UAV project.
According to research published in the journal Science, it could be used for everything from environmental monitoring, search-and-rescue operations, to helping with crop pollination.
Its wafer-thin wings flap almost invisibly using two strips of ceramic that expand and contract as an electric field is switched on and off.
During tests, scientists controlling the RoboBee via a wire tether made it take off, hover, and change direction.
Each wing is attached to the top of an elongated carbon fibre body standing on wire legs.
Like those of a real fly, the wings move independently and can rotate as well as flap.
The beating wings create a downdraft that keeps the robot aloft, while forward and backward flight is achieved by tilting its body.
The mini-robot could be developed for environmental monitoring, search-and-rescue operations, or crop pollination. Before that can happen, though, it must be given a miniaturised computer "brain" and a battery pack small and light enough to be carried into the air.
Project leader Professor Robert Wood, from the Harvard School of Engineering and Applied Sciences, said: "It's really only because of this lab's recent breakthroughs in manufacturing, materials, and design that we have even been able to try this. And it just worked spectacularly well."