Nature gave ability to fly to birds, insects and some mammals quite some time ago. We, as a species, learned how to fly only very recently. And let's be honest here. We are not very good at it. We need machines to fly. Any our machines are not very efficient at that task. They require huge amounts of energy to do it, need maintenance and make a lot of noise. Look at birds and bats. They fly for longer using less energy. And they do it with grace.
This is project that caught my attention only today: mechanical bat from University of Illinois called Bat Bot B2.
Bat Bot, from Caltech von PopSci
Take a look at that video. Maybe it's not stable or capable of longer flights yet, but I'm really, really impressed. One day I would really like to have an UAV like that!