The pigments preserved in a 120 million year old fossil bird have been revealed using X-rays. A team scanned the beautifully preserved fossils of "Gansus yumenensis" and "Confuciusornis sanctus". Their study, published in the journal "Science", revealed the chemical fingerprint of pigments that once tinted the ancient bird's feathers. The trace metal copper is a marker for the dark pigment eumelanin. "The X-ray technique was so sensitive that it was able to show that each molecule of copper it detected was being tugged and squashed into a particular shape because it was bound within a eumelanin molecule".