http://www.nytimes.com/2014/01/16/science/with-math-as-inspiration-a-new-form-of-flyer.html?emc=eta1

The lightweight, electrically powered machine, which seems to be
the first of its kind, keeps itself right side up without the benefit of sensors
or any righting mechanism. Its stability is completely a result of its shape and
the movement of its three-inch wings.

“The aerodynamics involved in flapping wing flight are so complicated that we
can’t just make predictions,” Dr. Ristroph said. Instead, he explained, they
have to make physical models and see what happens.

Thanks to the Mad Scientist.