22 May 2014 Last updated at 01:25
By James Morgan
Science reporter, BBC News, Grenoble
The pinhole camera reveals hidden feathers inside the fossil slab
Is it a bird? Is it a dinosaur? Or something in between?
The feathered limbs of Archaeopteryx have fascinated palaeontologists ever since Charles Darwin's day.
Only 12 of these curious creatures have ever been found.
Now these precious fossils are going under the glare of a giant X-ray machine - to find out what lies buried beneath the surface.
Using a new "camera obscura" technique - inspired by Leonardo da Vinci - scientists have captured some of the clearest ever images ofArchaeopteryx.
For the first time, they can see the complete skeleton in 3D. Not just the surface outlines, but all the hidden bones and feathers too.
They hope to discover how "the first true birds" evolved from feathered dinosaurs and took flight.
And what's more, to answer a riddle that has puzzled palaeontologists for 150 years. Could Archaeopteryx fly, or not?